Vehicle Component and System Troubleshooting

GENERAL INFORMATION

For a description of electronic control system diagnostics and diagnostic trouble codes, refer to the Engine Electrical Systems section.

This section provides the simplest procedure for determining the causes of faults and failures occurring in vehicle components and systems. Faults and their possible causes are grouped by the component or system involved, such as the engine, cooling system, etc. In addition, the text provides references to the Sections and Subsections related to these problems.

Remember that successfully finding the cause of a fault is not black magic available only to experienced professional mechanics. It depends on a combination of specific knowledge and a patient, systematic approach to investigating the problem. Always proceed from simple to complex, carry each check through to its logical conclusion, and try not to overlook obvious facts. Anyone can forget to fill the fuel tank or leave the lights on overnight.

Finally, always try to form a clear picture of how the fault developed and take appropriate steps to prevent it from recurring. If an electrical failure was caused by a poor connection, also check the condition of all other connections and electrical connectors in the system. If the same fuse keeps blowing repeatedly, there is no point in simply replacing it again; try to determine the cause of the failure. Remember that failure of a minor component may be a sign of a malfunction in a more important unit or an entire system.

Engine

If the engine does not start, analyze the situation. For the engine to start at all, two basic conditions must be met. A combustible air-fuel mixture must enter the cylinders, and the spark plugs must produce a spark. Therefore, first, check whether fuel is being supplied. For the procedure, refer to the Fuel and Exhaust Systems section.

To determine whether a spark is being produced, remove all spark plugs, insert them into the spark plug connectors and ground them individually against the engine. Note: To prevent damage to the catalytic converter, disable fuel injection during this check. To do so, disconnect the electrical connectors of the fuel injectors. If there is no spark, diagnose the fault according to the Engine Electrical Systems section.

CAUTION

Observe safety precautions when working on the electronic ignition system (refer to Engine Electrical Systems section).

Do not hold the spark plug connector or ignition cable by hand; use well-insulated pliers. Ask an assistant to crank the engine. If no spark jumps the gap, diagnose the fault using the Engine Electrical Systems section.

The engine does not crank when attempting to start

1. Battery terminals are corroded or the wire connectors are loose on the terminals. Inspect the condition of the terminals and connectors. Tighten the terminal clamps and clean off any corrosion if necessary.

2. Battery is discharged or faulty. If the wire connectors are found clean and securely attached to the battery terminals, turn the ignition key to the ON position, then switch on the headlights and/or windshield wipers. If these electrical components do not operate, the battery is discharged.

3. Transmission is not correctly set to “P” (AT) or to neutral (MT), or the clutch pedal is not fully depressed.

4. Wiring in the starter circuit is broken or the wire connections at the terminals are loose. Check whether voltage of at least 10 V is present at terminal 50 of the starter solenoid during cranking, which is required for solenoid engagement. Check the condition of the wires, terminals and electrical connectors of the battery, starter solenoid and ignition switch.

5. Starter pinion is jammed in the flywheel ring gear. On vehicles equipped with a manual transmission, engage a gear and rock the vehicle by hand to turn the engine over. At the first opportunity, remove the starter and inspect the condition of the pinion and the flywheel ring gear.

6. Starter solenoid is faulty (refer to the Engine Electrical Systems section).

7. Starter motor is faulty (refer to the Engine Electrical Systems section).

8. Ignition switch is faulty.

The engine cranks but does not start

1. Starting procedure is incorrect.

Gasoline engine starting procedure:

Apply the parking brake and fully depress the clutch pedal. On vehicles with AT, press and hold the brake pedal. On AT, set the selector to “P” or “N”. Do not depress the accelerator pedal. Turn the ignition key and hold it until the engine starts. If the engine does not start within 20 s or stalls immediately, repeat the starting process with the accelerator pedal depressed halfway. As soon as the engine starts, release the ignition key.

At temperatures below –15°C and at altitudes above 1000 m above sea level: Crank the engine for no more than 10 s with the accelerator pedal depressed halfway. Be sure to start driving immediately. In severe cold, let the engine run for 30 s.

If the engine does not start, stop cranking after 10 s and repeat the attempt after half a minute.

CAUTION

Several consecutive unsuccessful start attempts may damage the catalytic converter, because unburned fuel explosively combusts when heated in the catalytic converter.

Only on a warm engine, slightly increase the throttle after starting.

2. Engine immobilizer is faulty.

3. Fuse is faulty:

– electric fuel pump; – electronic fuel injection system.

For fuse inspection, refer to the Fuses subsection.

4. Fuel tank is empty or poor-quality fuel has been added.

5. Air filter is heavily contaminated. Vacuum leaks in the air intake components, faults in the fuel injection and ignition control system.

6. Battery is discharged (engine cranks too slowly). Check the operation of the electrical system.

7. Battery terminal connections are corroded or loose (refer to the previous section).

8. Fuel pump is faulty.

9. Ignition system components are damaged or excessively wet (refer to the Engine Electrical Systems section).

10. Spark plugs are worn or faulty, or the spark plug gap is incorrectly set (refer to the Engine Electrical Systems section).

11. Starter circuit wiring is broken or disconnected, or the wire connections at the terminals are loose.

12. Ignition coil circuit wiring is broken or disconnected, or the wire connections at the coil terminals are loose (refer to the Engine Electrical Systems section).

13. Compression pressure is too low. Replace the cylinder head gasket. Repair the engine if necessary. Diesel engine:

14. Starting procedure is incorrect. Turbo diesel engine starting procedure:

With a cold engine and outside temperature below +8°C, apply the parking brake and fully depress the clutch pedal. On AT, set the selector to “P” or “N”; on MT, neutral. Turn the ignition key to position II and wait until the glow plug indicator light goes out. Immediately after the light goes out, start the engine without depressing the accelerator. If irregular firing occurs, do not release the starter until the engine runs smoothly (no more than 30 s). If the engine does not start, wait half a minute and repeat the start as described above. Do not switch on electrical consumers (lights, rear window defroster) during glow plug preheating.

With a cold engine and outside temperature above +8°C, or with a warm engine, glow plug preheating is not required. The engine can be started immediately. Do not depress the accelerator.

15. Engine immobilizer is faulty.

16. Fuse is faulty:

– electric fuel pump; – glow plug system.

17. Engine is not warmed up: check the glow plug device for proper operation.

18. There is no voltage at the solenoid shut-off valve. Connect a voltmeter or an LED test light to the switch. Turn the ignition on. The LED should light up. Otherwise, locate and repair the open circuit in the wiring.

19. The solenoid shut-off valve is faulty. Check the solenoid switch mounting and check the contacts. Turn the ignition on and off. A click should be heard from the switch.

20. Fuel supply line damage or air in the lines:

a) Fuel lines or hoses are mechanically damaged or clogged. Clean the fuel lines and bleed air from the lines and filter. b) Fuel filter is clogged. Replace the filter element. c) In winter, check the filter and lines for ice or wax. Park the vehicle in a heated garage and add gasoline to the system. d) Fuel tank vent or fuel pick-up strainer is clogged.

Clean.

21. Fuel injection timing is out of adjustment. Check and adjust.

22. Injectors are faulty. Check. Loosen the union nuts one at a time. Engine speed will not drop when the nut of the faulty cylinder is loosened.

23. High-pressure fuel injection pump (HPFIP) is faulty. Install a new or known-good HPFIP for testing.

24. Compression pressure is too low. Replace the cylinder head gasket. Repair the engine if necessary.

Starter operates without cranking the engine

1. Starter pinion is jammed. Remove the starter (refer to Engine Electrical System) and check its condition.

2. Starter pinion or flywheel ring gear teeth are worn or damaged.

Difficult starting of a cold engine

1. Battery is discharged or insufficiently charged.

2. Fault in the fuel system components or electrical equipment.

3. Paraffin in the fine fuel filter of the diesel engine. Replace the filter element. Fill with winter diesel fuel or dilute with gasoline.

4. Glow plugs of the diesel engine are faulty.

Difficult starting of a hot engine

1. Air filter is clogged.

2. Fault in the fuel system components or electrical equipment.

3. Fuel does not reach the injectors of the injection system.

4. Diesel engine fuel injection timing has shifted.

5. Low compression in the cylinders, or the HPFIP of the diesel engine is faulty or out of adjustment.

Starter engagement is too noisy or difficult

1. Starter pinion or flywheel ring gear teeth are worn or damaged.

2. Starter mounting bolts are lost or their tightening torque has weakened.

Engine starts but stalls immediately

1. Engine immobilizer is faulty.

2. Wiring is faulty, or wire connections at the ignition coil or alternator terminals are loose.

3. Fault in the fuel system components or electrical equipment.

4. Basic settings of the Electronic Control Module (ECM) are incorrect.

5. Damage in the exhaust system / catalytic converter.

6. Vacuum leaks at the intake manifold or fuel injection unit mating surfaces. Make sure the mounting bolts/nuts are tightened securely. Check that all vacuum hoses are properly and securely connected to their intake manifold fittings. Check the condition of the hoses and confirm they are connected to the correct fittings.

Unstable engine operation at idle

1. Vacuum leaks. Make sure the mounting bolts/nuts are tightened securely. Check that all vacuum hoses are properly and securely connected to their intake manifold fittings. Listen to the running engine with a stethoscope or a length of fuel hose. A hissing sound indicates the source of the vacuum leak. A soapy water solution can also be used effectively for checking.

2. Fault in the fuel system components or electrical equipment.

3. Positive Crankcase Ventilation (PCV) valve is clogged.

4. Air filter is clogged.

5. Fuel pump does not supply sufficient fuel to the injectors of the injection system.

6. Leaks through the cylinder head gasket. Measure the compression pressure in the engine cylinders.

7. Worn camshaft lobes. Diesel engine:

8. Fuel hose connections at the HPFIP and fuel filter are faulty. Replace the fuel hoses, secure them with clamps, and tighten the banjo bolts.

9. HPFIP is mechanically damaged or its mounting is loose. Check the mounting.

10. Return line and fuel supply line connections are swapped. Reconnect the connections to their correct positions. The return line connection bolt is marked "OUT".

11. Fuel supply line damage:

a) Fuel lines or hoses are mechanically damaged or clogged. Clean the fuel lines. b) Fuel filter is clogged. Replace the filter element. c) In winter, check the filter and lines for ice or wax. Park the vehicle in a heated garage and add gasoline to the system. d) Fuel tank vent or fuel pick-up strainer is clogged.

Clean.

12. Fuel injection timing is out of adjustment. Check and adjust.

13. Injectors are faulty. Check. Loosen the union nuts one at a time. Engine speed will not drop when the nut of the faulty cylinder is loosened.

14. High-pressure fuel injection pump (HPFIP) is faulty. Install a new or known-good HPFIP for testing.

Misfiring occurs with the engine running at idle

1. Spark plugs are worn or dirty, or the spark plug gap is incorrect (refer to Engine Electrical System).

2. Fault in the fuel system components or electrical equipment.

3. Spark plug wires are faulty (refer to Engine Electrical System).

4. Low-quality fuel was added. Fuel filter is clogged.

5. Vacuum leaks in the intake manifold or at the hose connections.

6. Compression pressure in the cylinders is insufficient or unevenly distributed. Measure the compression.

7. Malfunction of the engine management system.

Misfiring occurs while driving in gear.

1. Fuel filter is clogged or the fuel system is contaminated.

2. Spark plugs are faulty or dirty, or the spark plug gap is incorrect (Refer to Engine Electrical System section).

3. Fault in the fuel system components or electrical equipment.

4. Spark plug wires are defective (Refer to Engine Electrical System section).

5. Exhaust emission control system components are faulty.

6. Compression pressure is low or uneven between cylinders. Remove the spark plugs and measure the compression pressure.

7. Ignition system is faulty (Refer to Engine Electrical System section).

8. Vacuum leaks at the throttle body, intake manifold, or vacuum hoses.

Engine stalls.

1. Idle speed adjustment is incorrect.

2. Fuel filter is clogged and/or water or dirt has entered the fuel system.

3. Fuel system components or sensors are faulty.

4. Exhaust emission control system components are faulty.

5. Spark plugs are faulty or dirty, or the spark plug gap is incorrect. Also check the condition of the spark plug wires (Refer to Engine Electrical System section).

6. Vacuum leaks at the throttle body or through the vacuum hoses.

Engine does not produce full power.

1. Fuel system or electrical component malfunction (Refer to Engine Electrical System section).

2. Air cleaner is clogged. Clean or replace.

3. Spark plugs are faulty or the spark plug gap is incorrect.

4. Ignition coil is faulty (Refer to Engine Electrical System section).

5. Automatic transmission fluid level is not within specification.

6. Clutch is slipping.

7. Fuel filter is clogged and/or dirt/water has entered the fuel system.

8. Wrong fuel grade was used. Fill the tank with fuel of the specified octane rating.

9. Turbocharger wastegate control valve is damaged.

10. Timing camshaft phase shifter actuator is faulty.

11. Compression pressure is low or uneven between cylinders. Measure compression and analyze the results to identify valve leakage and/or cylinder head gasket leakage. Additionally for diesel engine:

12. Air cleaner is clogged. Clean or replace.

13. Uneven fuel delivery between cylinders by the injection pump. Adjust with the engine warm.

14. Injection pump start-of-injection timing is incorrect. Adjust.

15. Fuel filter or injection pump (injector) is clogged. Clean the pre-filter, replace the fine filter element, clean the nozzle, or replace the pump (injector).

16. Maximum crankshaft speed adjustment is incorrect.

Backfiring in the intake system or popping in the exhaust system occurs.

1. Fuel system or electrical component malfunction (Refer to Engine Electrical System section).

2. Secondary ignition circuit defect (spark plug insulator damage or spark plug wire defects) (Refer to Engine Electrical System section).

3. Fuel injection system requires adjustment or its components are excessively worn.

4. Vacuum leaks at the throttle body, intake manifold, or vacuum hoses.

5. Valves are stuck.

6. Spark plug wire connection sequence is incorrect (Refer to Engine Electrical System section).

Detonation sounds occur during acceleration or uphill driving.

1. Low-quality fuel was used.

2. Fuel system or electrical component malfunction (Refer to Engine Electrical System section).

3. Spark plugs of an incorrect type are installed. Check the spark plugs and coils for damage (Refer to Engine Electrical System section).

4. Engine control unit basic settings are incorrect.

5. Knock sensor is faulty.

6. Vacuum leaks occur.

Dieseling occurs (engine keeps running after the ignition is switched off).

1. Idle speed is excessively high.

2. Fuel system or electrical component malfunction (Refer to Engine Electrical System section).

3. Evaporative emission (EVAP) canister purge valve is damaged.

4. Engine operating temperature is excessive. Possible causes include low coolant level, thermostat failure, radiator blockage, or water pump malfunction.

Diesel engine emits smoke.

1. Black smoke:

a) Air cleaner is contaminated. Wash and recharge with fresh oil, or replace the element. b) Incorrect fuel was used. Flush the tank and replace the fuel. c) Injection pump start-of-injection timing is incorrect.

2. Blue smoke:

a) Oil burning in the combustion chamber due to worn piston rings, high oil level in the air cleaner, worn turbocharger seals, or a leaking gasket between the cylinder block and turbocharger. Repair the engine, set the oil level to normal, replace the seals, tighten the turbocharger mounting bolts, or replace the gasket. b) Fuel is not supplied to one of the injectors. Check by the heat of the exhaust manifold outlets. c) Poor fuel atomization by an injector due to a faulty valve or broken nozzle. Lap the valve or replace the injector.

3. White or brown smoke:

a) Low temperature in the cooling system. Check the thermostat. b) Poor injector operation due to wear or a broken nozzle tip. Replace the nozzle.

Engine Electrical Equipment

Battery does not hold charge.

1. Alternator drive belt is worn or damaged, or its tension is incorrect (Refer to Engine Electrical System section).

2. Electrolyte level is low or the battery is severely discharged (Refer to Engine Electrical System section).

3. Battery terminals are corroded or the wire terminal connections are loose (Refer to Engine Electrical System section).

4. Alternator does not provide the required charging current (Refer to Engine Electrical System section).

5. Charging circuit wiring is broken or otherwise damaged, or wire connections at the terminals are loose.

6. A short circuit in the wiring causes a constant leakage of battery current to ground

7. Internal battery defect.

Charge warning lamp does not go out when engine speed increases

1. Drive belt is loose. Check the V-belt tensioner.

2. Overrunning alternator decoupler pulley damaged (turbocharged diesel only). Remove the alternator and turn the alternator drive shaft counterclockwise. If the pulley working surface does not rotate, the decoupler is generally damaged.

3. Voltage regulator/alternator defective. Disconnect the (D+) wire from the back of the alternator and turn the ignition on. If the warning lamp does not illuminate, the voltage regulator or alternator is generally at fault.

4. Brushes worn. Visually inspect the brushes and replace if necessary.

5. Regulator defective. Inspect and replace if necessary.

6. Alternator defective. Inspect and replace if necessary.

7. Wire between alternator and voltage regulator damaged. Disconnect the blue wire at terminal 12 of connector T32a and at the instrument panel unit. If the warning lamp still does not illuminate, the D+ wire is shorted to ground. Replace the harness.

8. Instrument panel unit defective. If the warning lamp illuminates with the ignition on after disconnecting the blue wire from connector T32a, the fault is generally in the instrument panel unit.

Charge warning lamp does not illuminate when the ignition key is turned to the "ON" position

1. Charge warning lamp on the instrument panel burned out or otherwise failed

2. Alternator defective

3. Defect in the printed circuit board, wiring inside the instrument cluster or lamp socket

Charge warning lamp remains on after the ignition is switched off

Positive diodes shorted. Check the diodes and replace the diode plate.

Starter

If the starter does not crank, first check that terminal 50 of the starter relay has the required voltage, at least 10 V. If the voltage is below this value, check the wiring in the starter circuit according to the wiring diagram.

To check whether the starter operates at full battery voltage, proceed as follows:

– without engaging a gear, turn the ignition on. – Jumper starter terminals 30 and 50 with a wire of at least 4 mm². Also refer to the section "Starter Solenoid Test".

If the starter operates correctly, the cause of the fault is in the starter wiring. If the starter does not operate, it must be checked after removal.

Check condition: Wire connections must be secure and free of corrosion.

Starter does not crank when the ignition switch is turned

1. Battery discharged. Charge the battery.

2. Jumper starter terminals 30 and 50: starter cranks. Open circuit in wire 50 to the ignition switch, or starter switch defective. Repair the open circuit and replace defective parts.

3. Open circuit in ground cable or connector, battery discharged. Check the battery cables and connectors, measure battery voltage, and charge if necessary.

4. Insufficient current flow due to loose or corroded connectors. Clean the battery terminals and posts, and check the connections between the battery, starter, and ground.

5. No voltage at terminal 50 of the starter relay. Open circuit in wire, starter switch defective.

Starter cranks slowly and does not turn the crankshaft

1. Battery discharged. Charge the battery.

2. Summer oil in engine. Fill with multigrade oil.

3. Insufficient current flow due to loose or corroded connectors. Clean the battery terminals and posts, and check the connections between the battery, starter, and ground.

4. Carbon brushes not contacting the commutator, sticking in their guides, worn, broken, oily, or dirty. Check the brushes, clean or replace them. Check the brush guides.

5. Insufficient brush-to-commutator clearance. Replace the brushes and clean the brush guides.

6. Commutator grooved, or burnt and oily. Resurface the commutator or replace the armature.

7. No voltage at terminal 50 (min. 8 V). Check the starter switch or the solenoid relay.

8. Bearing damaged. Inspect the bearing and replace if necessary.

9. Solenoid relay defective. Replace the solenoid relay.

Starter engages and cranks the engine in jerks

1. Pinion drive defective. Replace the pinion drive.

2. Pinion dirty. Clean the pinion.

3. Flywheel ring gear defective. Resurface the ring gear or replace the flywheel if necessary.

Starter pinion does not disengage from the ring gear

1. Pinion drive or thread dirty or damaged. Clean or replace the pinion drive.

2. Solenoid relay defective. Replace the solenoid relay.

3. Return spring weakened or broken. Replace the return spring.

Starter keeps running after the ignition key is released

1. Solenoid relay stuck and not releasing. Turn the ignition off immediately and replace the solenoid relay.

2. Ignition switch does not release. Disconnect the battery immediately and replace the ignition switch.

Fuel System

Excessive fuel consumption

1. Air filter element dirty or clogged.

2. Fault in the fuel system, electrical equipment, or electronic control components.

3. Air leaks in the intake system.

4. Exhaust system/catalytic converter damaged.

5. Tire pressure too low or incorrect tire size fitted. Diesel engine

6. Return line clogged. Blow out the return line from the injection pump to the fuel tank with compressed air.

7. Idle speed and maximum speed too high. Adjust.

8. Engine mechanically damaged. Check compression and repair the engine if necessary.

Fuel leaks and/or smell of gasoline

1. Leaks in fuel supply lines or vent lines

2. Fuel tank overfilled. Fill only until the nozzle shuts off automatically.

3. Leaks or evaporation from the fuel system and emission control lines

Engine does not start

1. When the starter is operated, the electric fuel pump does not run (no operating noise is heard). Lightly tap the pump housing to free a stuck component. Check whether voltage is supplied to the pump. Check the fuse for proper condition. Check the electrical contacts for good conductivity.

2. Fuel pump relay is faulty. Check the relay.

3. Injector valves are stuck. Check the injectors and replace if necessary. Check the voltage supply to the injectors. To do this, disconnect the injector connector. Connect a diode test lamp to the wire and operate the starter. The test lamp should flash.

4. No signal from the ignition timing sensor or the engine speed sensor. Check the electrical wires. Read the fault memory.

5. Fuel lines are damaged, clogged or leaking. Hoses are defective.

6. Fuel filter is clogged.

7. Ice or wax in the filter or lines of the diesel engine.

8. Fuel tank vent is blocked, fuel tank filter is clogged.

9. Diesel engine injectors are damaged. Loosen the union nuts one at a time and check whether the corresponding cylinder operates.

Cold engine starts poorly and runs unevenly

1. CO content does not meet requirements. Check the CO content and idle speed.

2. Temperature sensor is faulty. Check the engine coolant/intake air temperature sensor.

3. Fuel pressure does not meet the specified value. Check the fuel pressure.

Warm engine starts poorly and runs unevenly

1. Air intake system leaks. Check the intake system. To do this, let the engine run at idle and spray gasoline on the seals and connections of the intake tract. If engine speed briefly increases, eliminate the leaks.

CAUTION

Gasoline vapors are poisonous. Do not inhale them.

Engine misfires

1. Electrical connections to the fuel pump intermittently open. Check the plug connections and electrical wire connectors of the fuel pump, air flow meter and fuel pump relay. Check the fuse and the contacts of the fuel pump relay. Clean the contacts; replace if necessary.

2. Poor fuel quality, vapor lock. Fill with good-quality fuel.

3. Fuel delivery volume is too low. Check the pump capacity.

4. Fuel filter is faulty. Replace the fuel filter.

5. Fuel pump is faulty. Check the fuel pump.

6. Injectors are faulty. Check the injectors.

7. Throttle position sensor is faulty. Check the throttle position sensor.

8. Fuel hoses are loose at the diesel injection pump and fuel filter.

Engine misfires during transient conditions and at idle

1. Air intake system leaks. Check the intake system connections. Start the engine and spray gasoline on the contact points and connections in the intake tract. If engine speed briefly increases, eliminate the leak.

2. Idle speed adjustment is incorrect. Check the idle air control valve, throttle position sensor and lambda control.

3. Full load sensor is faulty or incorrectly adjusted. Check the throttle sensor.

Hot engine does not start

1. CO content is incorrectly adjusted. Check the CO content and idle speed.

2. Fuel system pressure is too high. Check the fuel pressure; replace the pressure regulator if necessary.

3. Return line between the pressure regulator and the fuel tank is clogged or bent. Clean or replace the line.

4. Engine temperature sensor is faulty. Check the temperature sensor.

5. Fuel system leaks. Visually inspect all connections in the engine area and the electric fuel pump. Tighten all connections.

6. Air intake system leaks. Check all intake system connections.

Engine runs after switch-off

1. Injectors are leaking. Check the injectors.

2. Fuel shut-off valve on the diesel engine is not working.

Lubrication System

Warning lamp does not light after ignition is switched on

1. Oil pressure sensor is faulty. Switch on the ignition, disconnect the wire from the oil pressure sensor and ground it. If the lamp lights, replace the sensor.

2. No voltage to the sensor, contacts are corroded. Check the electrical wires and contacts.

3. Warning lamp is faulty. Replace the warning lamp.

4. Control module is faulty. Replace the control module.

Warning lamp does not go out after engine start

Oil is overheated. If the warning lamp goes out after accelerating, no action is required.

Warning lamp does not go out after accelerating or comes on while driving

1. Oil pressure is too low. Check the oil level and top up if necessary. Check the oil pressure.

2. Oil pressure sensor wire is shorted to ground. Disconnect the cable from the sensor and move it aside (without grounding), switch on the ignition. If the lamp lights, check the wire.

3. Oil pressure sensor is faulty. Replace the sensor.

Oil pressure is too low at all engine speeds

1. Engine oil level is too low. Top up the oil.

2. Oil strainer is clogged. Remove the oil pan and clean the oil strainer.

3. Oil pump is worn. Remove the oil pump, inspect it and replace if necessary.

4. Bearing damage. Remove the engine.

Oil pressure is too low at low engine speeds

Pressure relief valve is stuck open due to contamination. Remove and inspect the valve.

Oil pressure is too high at engine speeds above 2000 rpm

Pressure relief valve does not open due to contamination. Remove and inspect the valve.

Cooling System

Overheating

1. Insufficient coolant in the system

2. Water pump drive belt is worn or damaged, or its tension is incorrectly adjusted

3. Internal radiator passages are blocked or the radiator grille is contaminated (obstructed)

4. Thermostat is faulty

5. Fan blades are broken or cracked

6. Fan clutch is faulty. Check the fan clutch: Increase the engine speed with the engine warmed up. As soon as the coolant temperature reaches 90 – 95°C, the fan speed will increase, which can be heard.

7. Coolant temperature gauge is faulty. Check the sensor.

8. Coolant pump is faulty. Remove and check the pump.

9. Radiator cap does not hold pressure. Check the cap pressure (contact a service station).

Overcooling

1. Thermostat is faulty

2. Coolant temperature gauge readings are inaccurate.

External coolant leaks

1. Hoses are damaged or deteriorated due to aging, or hose clamps at the connections are loose. Replace the hoses and/or tighten the hose clamps

2. Water pump seals are damaged. In this case, coolant will seep through the inspection hole in the pump housing

3. Leaks from the internal passages of the radiator or side tank(s). Professional radiator repair is required

4. Leaks through the engine drain plug or water jacket drain plugs

Internal coolant leaks

CAUTION

Internal coolant leaks are usually detected by checking the condition of the engine oil. Inspect the dipstick blade and the inner surfaces of the cylinder head cover(s) for signs of water and oil foaming.

1. Leaks through the cylinder head gasket. Perform a cooling system pressure test.

2. Cracks in the cylinder walls or cylinder head casting. Disassemble the engine for inspection

Coolant loss

1. Too much coolant has been added to the system

2. Coolant boils off due to engine overheating

3. Internal or external coolant leaks are present

4. Radiator cap is faulty. Check the cap pressure.

Coolant circulation is disturbed

1. Water pump is not functioning properly. The easiest way to verify pump operation is to pinch the upper radiator hose with the engine running at idle. If you feel a surge of fluid inside the hose when you release it, the pump is working correctly

2. Cooling system passages are restricted. Drain the coolant, flush the system, and refill it with fresh mixture. If necessary, remove the radiator and perform reverse-flow flushing.

3. Water pump drive belt is worn or damaged, or its tension adjustment is incorrect

4. Thermostat is stuck

Heater

Heater fan does not operate

1. Fan motor fuse is faulty. Check the fan fuse and replace if necessary.

2. Fan switch is faulty. Check whether voltage is applied to the blower resistor, remove and check the fan switch.

3. Electric motor is faulty. With the ignition on and the fan switch closed, check whether voltage is applied to the fan motor terminals. If voltage is present, replace the motor.

Heater fan does not operate at one of the speeds

Blower resistor is faulty. Replace the connection board.

Heater cannot be turned off with the control

1. Switch is faulty. Check the switch.

2. Blend door control cables are damaged or do not move freely. Replace the cables.

Heating output is too low

1. Coolant level is too low. Check the coolant level and top up if necessary.

2. Heater control unit is stiff or faulty. Check the heater control unit and replace the cable if necessary.

Noise from the heater fan area

1. Dirt or leaves have entered. Remove the fan and clean it, clean the air duct.

2. Impeller imbalance, bearing fault. Remove the fan motor and check for smooth operation.

Clutch

Clutch does not disengage (the manual transmission shift lever does not move freely into and out of reverse with the clutch pedal fully depressed)

Clutch disc is bent or damaged

Clutch slips (engine speed rises without an increase in vehicle speed)

1. Clutch disc is contaminated with oil or its friction linings are worn. Remove the clutch and inspect its components.

2. Clutch disc has not bedded in properly. Final bedding-in of a new disc may require 30 to 40 normal vehicle starts.

3. Pressure plate/clutch cover is worn

Severe vibration when the clutch is engaged

1. Clutch disc is oil-contaminated. Remove the clutch and inspect its components. Repair all leaks found.

2. Clutch disc hub splines are worn. Remove the clutch and inspect its components.

3. Pressure plate/clutch cover or flywheel is bent. Remove the clutch and inspect its components and the flywheel.

Judder when operating the clutch

1. Engine and transmission mounts are damaged. Inspect and replace if necessary.

2. Transmission mounting bolts in the suspension are loose. Tighten the mounting bolts.

3. Uneven contact of the pressure plate. Replace the clutch cover.

4. Crankshaft is not aligned with the transmission. Check the alignment.

Squeal or rumble when the clutch is fully engaged (pedal released)

Clutch release bearing is seized. Remove the clutch and inspect the bearing. Remove all burrs and scoring, and lubricate the bearing before installation.

Squeal or rumble when the clutch is fully disengaged (pedal depressed)

1. Release bearing is worn or damaged

2. Clutch cover springs (or diaphragm fingers) are worn or damaged

Clutch pedal stays on the floor after release

Clutch master or slave cylinder piston is seized. Hydraulic clutch system or release bearing is damaged. Check the condition and remove the clutch components if necessary.

Manual Transmission (MT)

Abnormal noises occur with the transmission in neutral while the engine is running

1. Input shaft bearing is worn.

2. Output shaft drive gear bearing is damaged.

3. Countershaft bearings are worn.

4. Countershaft end-play adjustment washers are worn or damaged.

Abnormal noises occur in any gear position of the manual transmission

1. Any of the causes listed above and/or:

2. Insufficient transmission oil in the transaxle (oil level has dropped).

Abnormal noise occurs in a specific gear.

1. Worn, damaged, or chipped teeth on the gear of that speed.

2. Worn or damaged synchronizer for that gear.

Transmission "jumps out" of top gear.

Dirt has entered between the transmission case and the engine, or the transmission has shifted relative to the engine.

Difficulty occurs when shifting gears.

1. Clutch not fully depressed (disengaged).

2. Shift linkage is damaged, its attachment is loose, or its adjustment is incorrect. Carefully inspect the condition of the components and replace any defective parts as necessary.

Transmission oil leaks are present.

1. Excessive transmission oil has been filled into the transaxle. If necessary, drain the excess.

2. Differential oil seals need to be replaced.

Automatic Transmission (AT)

CAUTION

Due to the complexity of the design, complete troubleshooting and repair of AT components is beyond the capability of the average home mechanic. If any automatic transmission problems occur other than those listed below, have the vehicle inspected and repaired at a service workshop or an AUDI A3 dealership.

General problems related to shift mechanism operation

Malfunctions related to incorrect shift linkage adjustment include the following:

a) Engine can be started with the transmission in a position other than "P" (Park) or "N" (Neutral). b) Transmission position indicator does not match the actually selected gear. c) Vehicle moves with the transmission in the "P" position.

Adjust the shift linkage.

Transmission slips, shifts with difficulty, makes abnormal noise, or fails to propel the vehicle when placed in forward or reverse gear.

1. There are many possible causes for the problems listed in the heading, however only one of them is within the competence of a home mechanic: incorrect transmission fluid level.

2. Before taking the vehicle to a service shop, check the transmission fluid level and condition (Chapter 1). Correct the level in accordance with the Specifications or change the fluid together with the filter. If the problem is not resolved, consult a specialist.

Transmission fluid leaks are present.

1. AT fluid is dark red in color. Do not confuse fluid leaks with engine oil that may be blown onto the transmission case by the oncoming airflow.

2. To identify and locate the source of the leak, first clean all dirt and grease from the transaxle housing. Use a suitable degreaser and/or steam clean. Then make a short drive at low speed (so that leaking fluid is not blown far from its source). Stop, raise the vehicle, and visually inspect to determine the source of the leak. The most common sources are:

a) Transmission oil pan: Tighten the mounting bolts and/or replace the pan gasket. b) Fluid fill tube: Replace the rubber seal where the tube enters the transmission case. c) Transmission fluid lines: Tighten the fittings or replace the lines. d) Vent tube: Transmission is overfilled and/or water has entered the transmission.

Axles

Abnormal noise

1. Normal road noise. Cannot be corrected.

2. Tire noise. Check the tread condition and tire inflation pressure.

3. Wheel bearings are worn or damaged, or their preload has loosened.

Vibration

Check the condition of the wheel bearings by raising each corner of the vehicle in turn and rotating the wheel by hand. Listen for sounds coming from the bearing. Remove the bearings and check their condition.

Oil leaks

Driveshaft oil seals are damaged.

Brake System

CAUTION

Before reaching a final conclusion about a brake system problem, make sure the tires are in satisfactory condition and inflated to the specified pressure, the front wheel alignment angles are correctly set, and the vehicle is not loaded unevenly.

Increased brake pedal travel

Brake circuit has failed. Check for brake fluid leakage.

Brake pedal is spongy and sinks to the floor.

1. Air in the brake system. Bleed air from the system.

2. Insufficient fluid in the reservoir. Add new brake fluid and bleed air from the system.

3. Vapor bubbles forming. Occurs mainly under heavy brake use. Replace the brake fluid and bleed air from the system.

Reduced braking effect, pedal sinks.

1. Leaking brake line. Tighten the line connections or replace the lines.

2. Seals in the master or wheel cylinders are damaged. Replace the seal. In the master cylinder, replace the internal components; replace the master cylinder if necessary.

3. Rubber seal is damaged. Repair the caliper.

Poor braking despite high pedal force.

1. Brake pads are contaminated with oil. Replace the brake pads.

2. Unsuitable or hardened pads are installed. Replace the pads. Install genuine AUDI pads.

3. Brake booster is faulty. Inspect the brake booster.

4. Brake pads are worn. Replace the brake pads.

Vehicle pulls to one side when braking.

1. Tire pressure does not meet specification. Check and adjust tire pressure.

2. Uneven tire wear. Replace worn tires.

3. Brake pads are contaminated with oil. Replace the pads.

4. Different brake pads are installed on the same axle. Replace the pads. Install genuine AUDI pads.

5. Brake pads are in poor condition. Replace the pads.

6. Caliper guide bores are contaminated. Clean the guides and pad seating surfaces in the caliper.

7. Corrosion of the brake caliper cylinders. Replace the caliper.

8. Uneven brake pad wear. Replace the brake pads (on both wheels).

Brake drags on its own.

1. Compensating port in the master cylinder is clogged. Clean the master cylinder and replace the internal components.

2. Clearance between the pushrod and the piston of the master cylinder is too small. Check the clearance.

Brakes overheat during driving.

1. Compensating port in the master cylinder is clogged. Clean the master cylinder and replace the internal components.

2. Clearance between the pushrod and the piston of the master cylinder is too small. Check the clearance.

3. Restrictor orifice in the special valve on the bottom is clogged. Clean the master brake cylinder, replace the internal components and the brake fluid.

Brake pedal vibration

1. Incorrect type of brake pads installed. Replace the pads and install genuine AUDI pads.

2. Brake disc corroded in places. Thoroughly grind the brake disc.

3. Brake disc has lateral runout. Machine or replace the disc.

Brake pads do not retract from the brake disc, wheel turns with difficulty by hand

Corrosion in brake caliper cylinders. Repair the caliper, replace if necessary.

Uneven brake pad wear

1. Incorrect type of brake pads installed. Replace the pads and install genuine AUDI pads.

2. Caliper contaminated. Clean the caliper bore.

3. Piston moves with difficulty. Eliminate the cause.

4. Brake system leaks. Check the brake system for leaks.

Wedge-shaped brake pad wear

1. Brake disc does not rotate parallel to the caliper. Check the caliper mounting surfaces.

2. Corrosion in calipers. Remove contamination.

3. Piston operates incorrectly. Check the piston position.

Brake squeal

1. Often caused by atmospheric conditions (air humidity). If squeal occurs after prolonged parking in high humidity and then disappears, no action is required.

2. Incorrect type of brake pads installed. Replace the pads and install genuine AUDI A3 pads, apply anti-squeal paste to the backing plates.

3. Brake disc does not rotate parallel to the caliper. Check the brake caliper mounting surfaces.

4. Caliper bore contaminated. Clean the caliper bore.

5. Pad retaining springs bent. Replace the retaining springs.

6. Pressure springs stretched. Replace the pressure springs.

Brake pedal pulsation

1. ABS is active. Normal, no action required.

2. Excessive lateral runout or brake disc thickness variation. Check runout and thickness. Machine or replace the disc.

3. Brake disc does not rotate parallel to the caliper. Check the caliper mounting surface.

ABS warning lamp illuminates while driving

1. Supply voltage too low (below 10 V). Check the voltage. Check that the charging system warning lamp goes out after starting the engine. If everything is correct, check the generator drive V-belt.

2. ABS fault. Check the connection reliability and check the ground connection for corrosion at the return pump (in the hydraulic unit).

Suspension and Steering

Vehicle pulls to one side during driving SEQUENCE OF ACTIONS

1. Tires inflated unevenly.

2. Tire defect.

3. Suspension or steering components excessively worn.

4. Front wheel alignment adjustment required.

5. Front brake units seized.

Jerking, judder or vibration occurs

1. Wheel imbalance or wheel disc out-of-round. Balance the wheels at a tire service shop.

2. Wheel bearings worn, insufficient preload or incorrect adjustment.

3. Shock absorbers or other suspension components worn or damaged.

Excessive vehicle body sway or nose dive during cornering or braking

1. Shock absorbers faulty. Replace the complete set.

2. Springs and/or other suspension components broken or loose. Check the condition of the components.

Steering wheel turns too stiffly

1. Power steering fluid reservoir level excessively low.

2. Tires incorrectly inflated.

3. Steering linkage joints insufficiently lubricated.

4. Front wheel alignment incorrect.

5. Power steering does not develop required assist.

Excessive steering play

1. Front wheel bearing preload loose.

2. Suspension or steering components excessively worn.

Power steering system does not develop proper effort

1. Power steering pump drive belt worn or damaged, or belt tension incorrectly adjusted.

2. Hydraulic fluid level excessively low.

3. Hydraulic hoses or lines restricted. Check and replace if necessary.

4. Air in the hydraulic system. Bleed the system.

Excessive tread wear (not confined to one area)

1. Tires incorrectly inflated.

2. Wheel imbalance. Consult a tire service shop.

3. Wheel discs damaged. Check and replace if necessary.

4. Suspension or steering components excessively worn.

Excessive tread wear on the outer edge

1. Tires incorrectly inflated.

2. Turns made too sharply. Reduce speed.

3. Front wheel alignment incorrect (excessive toe-in). Have professional adjustment performed at a workshop.

4. Suspension control arm bent or twisted.

Excessive tread wear on the inner edge

1. Tires incorrectly inflated.

2. Front wheel alignment incorrect (toe-out). Have the adjustment performed at an automotive service shop.

3. Steering components damaged or mounting loose.

Localized tread wear

1. Wheel imbalance.

2. Wheel discs damaged or bent. Check and replace if necessary.

3. Tire defect.

Wiper blade defects

Skipping

1. Wiper blades contaminated. Clean the blades with a stiff nylon brush and detergent solution or alcohol.

2. Frayed blade edges, worn or torn wiper blades. Replace the blades.

3. Old blades, cracked surfaces. Replace the blades.

Water remains in the wiping area and immediately collects into droplets

Windshield contaminated with lacquer polish or oil. Clean the windshield with a clean cloth and a grease, oil and silicone remover.

Wiper clears one way only - works well in one direction but not the other

1. The wiper blade rubber is deformed in one direction and no longer returns to its position. Install a new wiper blade rubber.

2. The wiper arm is twisted and the blade does not contact the glass properly. Carefully turn the arm until it is in the vertical position.

Uncleaned surfaces

1. The rubber has come out of the frame. Carefully insert the rubber into the frame.

2. The blade contacts the glass unevenly because the spring strips or plates are bent. Replace the blade. This fault mainly occurs when a replacement blade is installed carelessly.

3. The arm pressure is too low. Lightly lubricate the wiper arm pivots and spring, or install a new arm.

Tire defects

Heavy tire wear on both shoulders of the tread face

Tire pressure too low.

Heavy tire wear in the center of the tread face, around the entire circumference

Tire pressure too high.

Uneven tread wear

Static and dynamic wheel imbalance. Possibly excessive wheel disc runout or excessive play in the wheel bearings.

Uneven wear in the center of the tread

Static wheel imbalance. Possibly the result of severe radial runout.

Heavy wear in individual areas in the center of the tread face

Signs of wheel lock-up during full braking.

Sawtooth tread wear. Often accompanied by a carcass ply separation that is not visible from the outside

Vehicle overloaded. Check the inside of the tire for carcass ply breaks.

Rubber lips on the outer edges of the tread

Incorrect wheel alignment angles. Tire worn. On the rear wheels, also check the condition of the shock absorbers.

Burrs formed on one side of the front tire tread

Incorrect toe-in adjustment. Tire worn. Frequent driving on wavy road surfaces. Fast cornering.

Cord breaks. Initially visible only from the inside

Driving over sharp stones, tire impacts, etc. at high speed.

Tread worn on one side only

1. Check the camber adjustment.

2. ABS fault. Check the ground connection to the body at the return pump (in the hydraulic unit).