Troubleshooting

Basic Troubleshooting Procedures

Basic Troubleshooting Procedure

Customer Problem Analysis Check Sheet

Basic Inspection Procedure: Resistance Measurement Conditions of Electronic Parts. Measured resistance may be high or low when the vehicle is hot after starting. Therefore, all resistances should be measured at ambient temperature (20 °C, 68°F), unless otherwise specified.

Measured resistance, except at ambient temperature (20 °C, 68°F), is for reference only.

Intermittent Problem Inspection Procedure: Sometimes the most difficult case in troubleshooting is when the symptom occurs but does not recur during testing. For example, the problem may appear only when the vehicle is cold and never when it is hot. In this case, the technician should carefully complete the "Customer Problem Analysis Sheet" and attempt to recreate (simulate) the environment and conditions under which the problem occurred.

1. 1
   Clear the Diagnostic Trouble Code (DTC).
2. 2
   Inspect all connections. Check the terminal for poor contact, loose wires, bent, broken, or corroded terminals, then make sure the connectors are always securely fastened.

   

3. 3
   Gently shake the connector and wiring harness vertically and horizontally.
4. 4
   Repair or replace the faulty component.
5. 5
   Perform a road test to confirm that the problem has disappeared.

● Simulate vibration

a.	Sensors and Actuators: Lightly tap the sensors, actuators, or relays with a finger. Strong vibration may damage sensors, actuators or relays.

b.	Connectors and Harness: Gently shake the connector and harness vertically, then horizontally.

● Simulate heat

a.	Heat the components suspected of causing the malfunction using a hair dryer or other heat source. DO NOT heat components to the point of damage. DO NOT heat the ECM directly.

● Simulate water spray

a.	Spray water on the vehicle to simulate a rainy day or high humidity condition. DO NOT spray water directly on the engine compartment or electronic components.

● Simulate electrical load

a.	Turn on all electrical systems to simulate excessive electrical load (radio, fans, lights, rear window defroster, etc.).

Connector Inspection Procedure

1. 1
   Connector Handling

   a.	Turn on all electrical systems to simulate excessive electrical load (radio, fans, lights, rear window defroster, etc.).

   b.	When disconnecting a connector with a lock, press or pull the lock lever.

   b.	Listen for a click when connectors lock. This sound indicates they are securely locked.

   d.	When using a tester to check continuity or measure voltage, always insert the tester probe from the wire harness side.

   e.	Check waterproof connector terminals from the connector side. Waterproof connectors cannot be accessed from the wire harness side. Use a thin wire to avoid damaging the terminal. Do not damage the terminal when inserting the tester probe.

2. 2
   Connector Checkpoints

   a.	While the connector is connected: Hold the connector and check the connection condition and locking effectiveness.

   b.	When the connector is disconnected: Check for loose terminals, crimped terminals, or broken core wires by gently pulling the wiring harness. Visually check for rust, contamination, deformation, and bending.

   b.	Check the terminal tightening condition: Insert a spare plug into the socket, then check the tightness of the terminals.

   d.	Gently pull on individual wires to make sure each wire is secured in the terminal.

3. 3
   Connector Repair Method

   a.	Clean the contact points using compressed air and/or a cloth. Never use sandpaper to polish the contact point, otherwise the contact point may be damaged.

   b.	If contact pressure is abnormal, replace the female terminal.

4. 4
   Before removing the harness, check the harness position and clamps so that it can be reinstalled correctly.
5. 5
   Check the wiring harness for twisted, stretched, or loose harness sections.
6. 6
   Check that the wire harness is not exposed to excessive temperature.
7. 7
   Check that the wiring harness does not rub, move, or vibrate against sharp edges of parts.
8. 8
   Check the connection between the wire harness and any installed part.
9. 9
   If the harness covering is damaged, secure, repair or replace the harness.
10. 10
    Open Circuit Procedures

    • Continuity Check
    • Voltage Check

    If an open circuit occurs (as shown in [FIG. 1]), it can be located by performing Step 2 (continuity check method) or Step 3 (voltage check method) as shown below.

    

11. 11
    Continuity Check Method

    When measuring resistance, gently shake the wiring harness vertically or horizontally.

    Specification (resistance): 1 Ω or less → Normal circuit; 1 MΩ or more → Open circuit

    a.

    Disconnect connectors (A) and (C) and measure the resistance between connectors (A) and (C), as shown in [FIG. 2]. In [FIG. 2], if the measured resistances on lines 1 and 2 are "more than 1 MΩ" and "less than 1 Ω" respectively, line 1 has an open circuit. (Line 2 is normal.) To find the exact point of the open, check the sub-section of line 1 as described in the following step.

    b.

    Disconnect connector (B) and measure the resistance between connectors (C) and (B1), and between (B2) and (A), as shown in [FIG. 3]. In this case, the measured resistance between connectors (C) and (B1) is more than 1 MΩ, and the open circuit is between terminal 1 of connector (C) and terminal 1 of connector (B1).

12. 12
    Voltage Check Method

    a.	With each connector still connected, measure the voltage between chassis ground and terminal 1 of each of connectors (A), (B), and (C), as shown in [FIG. 4]. The measured voltages at the connectors are 5V, 5V, and 0V respectively. Therefore, there is an open circuit between connectors (C) and (B).

13. 13
    Short to Ground Check Method

    • Continuity Check with Chassis Ground

    If a short to ground occurs (as shown in [FIG. 5]), the fault location can be found by performing Step 2 (continuity check method with ground) as shown below.

    

14. 14
    Continuity Check Method (with Chassis Ground)

    Gently shake the wiring harness vertically or horizontally while measuring resistance.

    Specification (resistance): 1 Ω or less → Short to ground; 1 MΩ or more → Normal circuit

    a.

    Disconnect connectors (A) and (C) and measure the resistance between connector (A) and body ground, as shown in [FIG. 6]. If the measured resistances on lines 1 and 2 are "less than 1 Ω" and "more than 1 MΩ" respectively, line 1 is open. (Line 2 is normal.) To find the exact point of the open, check the sub-section of line 1 as described in the following step.

    b.

    Disconnect connector (B) and measure the resistance between connector (A) and chassis ground, and between (B1) and chassis ground, as shown in [FIG. 7]. The measured resistance between connector (B1) and chassis ground is 1 ohm or less. A short to ground exists between terminal 1 of connector (C) and terminal 1 of connector (B1).

Wiring Harness Inspection Procedure: Electrical Circuit Inspection Procedure
● Open Circuit Test
● Short Circuit Test
● Voltage Drop Test. This test checks the voltage drop across a wire, connection, or switch.

A.	Connect the positive voltmeter lead to the end of the wire (or the connector or switch side) closest to the battery.

B.	Connect the negative wire to the other end of the wire (or to the other side of the connector or switch).

C.	Operate the circuit.

D.	The voltmeter will show the voltage difference between the two points. A drop of more than 0.1 V (50 mV in 5 V circuits) may indicate a problem. Check the circuit for loose or dirty connections.

Symptom Troubleshooting Table

Main Symptom	Diagnostic Procedure	Also check
Cannot Start (Engine does not crank)	1 Check the battery. (Refer to Engine Electrical System - "Battery") 2 Test the starter. (Refer to Engine Electrical System - "Starter") 3 Inhibitor switch (A/T) or clutch start switch (M/T)
Cannot Start (Incomplete combustion)	1 Check the battery. (Refer to Engine Electrical System - "Battery") 2 Inspect the fuel pressure. (Refer to Fuel System - "Fuel Pressure Inspection") 3 Check the ignition circuit. (Refer to Engine Electrical System - "Ignition System") 4 Troubleshoot the immobilizer system. (Refer to Body Electrical System - "Immobilizer System") (If the immobilizer lamp is flashing)	Trouble Code Low compression Intake air leaks Slipping or broken timing belt Contaminated Fuel
Hard to Start	1 Check the battery. (Refer to Engine Electrical System - "Battery") 2 Inspect the fuel pressure. (Refer to Fuel System - "Fuel Pressure Inspection") 3 Check the ECT sensor and circuit (check DTC) 4 Check the ignition circuit. (Refer to Engine Electrical System - "Ignition System")	Trouble Code Low compression Intake air leaks Contaminated Fuel Weak ignition spark
Poor Idling (Rough, unstable or incorrect idle)	1 Inspect the fuel pressure. (Refer to Fuel System - "Fuel Pressure Inspection") 2 Check the injector. (Refer to Engine Control System - "Injector") 3 Check the long-term fuel trim and short-term fuel trim. (See CUSTOMER DATA FLOW) 4 Inspect the idle speed control circuit. (Check the diagnostic trouble code.) 5 Inspect and check the throttle body. 6 Inspect the ECT sensor and its circuit. (Check the diagnostic trouble code.)	Trouble Code Low compression Intake air leaks Contaminated Fuel Weak ignition spark
Engine Stalls	1 Check the battery. (Refer to Engine Electrical System - "Battery") 2 Inspect the fuel pressure. (Refer to Fuel System - "Fuel Pressure Inspection") 3 Inspect the idle speed control circuit. (Check the diagnostic trouble code.) 4 Check the ignition circuit. (Refer to Engine Electrical System - "Ignition System") 5 Inspect the CKPS circuit. (Check the diagnostic trouble code.)	Trouble Code Intake air leaks Contaminated Fuel Weak ignition spark
Poor Driveability (Surging)	1 Inspect the fuel pressure. (Refer to Fuel System - "Fuel Pressure Inspection") 2 Inspect and check the throttle body. 3 Check the ignition circuit. (Refer to Engine Electrical System - "Ignition System") 4 Inspect the ECT sensor and its circuit. (Check the diagnostic trouble code.) 5 Check the exhaust system for possible clogging. (Refer to Engine Mechanical System - "Exhaust Manifold") 6 Check the long-term fuel trim and short-term fuel trim. (Refer to CUSTOMER DATASTREAM.)	Trouble Code Low compression Intake air leaks Contaminated Fuel Weak ignition spark
Knock	1 Inspect the fuel pressure. (Refer to Fuel System - "Fuel Pressure Inspection") 2 Inspect the engine coolant. (Refer to Engine Mechanical System - "Radiator") 3 Inspect the radiator and the cooling system electric fan. (Refer to Engine Mechanical System - "Radiator") 4 Check the spark plugs. (Refer to Engine Electrical System - "Ignition System")	Trouble Code Contaminated Fuel
Poor Fuel Economy	1 Check the customer's driving habits. · Is the A/C or defroster mode on constantly? · Is the tire pressure correct? · Is the vehicle carrying an excessively heavy load? · Is the acceleration too strong or too frequent? 2 Inspect the fuel pressure. (Refer to Fuel System - "Fuel Pressure Inspection") 3 Check the injector. (Refer to Engine Control System - "Injector") 4 Inspect the exhaust system for possible blockage. 5 Inspect the ECT sensor and its circuit.	Trouble Code Low compression Intake air leaks Contaminated Fuel Weak ignition spark
Hard to Refuel (Overflow during refueling)	1 Inspect the fuel tank hose/tube. · Pinched, kinked or blocked? · Torn filler hose 2 Inspect the fuel tank vapor hose between the EVAP canister and the air filter. 3 Inspect the EVAP canister.	Defective fuel filler nozzle at gas station (If this problem occurs at a specific gas station during refueling)