Troubleshooting

Basic Troubleshooting Procedures

Basic Troubleshooting Procedure

Customer Problem Analysis Check Sheet

Basic Inspection Procedure: Measuring Resistance of Electronic Parts. Resistance measured at high temperature after vehicle operation may be high or low. Therefore, all resistances must be measured at ambient temperature (20 °C, 68°F), unless otherwise specified.

Measured resistance values are reference values, except for ambient temperature (20 °C, 68°F).

Intermittent Problem Inspection Procedure: Sometimes the most difficult case in troubleshooting is when the problem symptom occurs but does not recur during testing. For example, if the problem occurs only when the vehicle is cold and did not appear when warm. In this case, the technician must carefully complete the Customer Problem Analysis Check Sheet and recreate (simulate) the environment and conditions present when the vehicle problem occurred.

1. 1
   Clear the Diagnostic Trouble Code (DTC).
2. 2
   Inspect the connector connection and check the terminal for poor contact. Check for loose connections, loose wires, bent, broken or corroded pins, then check that the connectors are always securely fastened.

   

3. 3
   Gently shake the connector and wire harness vertically and horizontally.
4. 4
   Repair or replace the faulty component.
5. 5
   Confirm that the problem is resolved by performing a road test.

● Simulate vibration

a.	Sensors and Actuators: Gently 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 wire 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 the components to the point where they may be damaged. DO NOT heat the ECM directly.

● Simulate water spray

a.	Spray water on the vehicle to simulate rainy or high humidity conditions. DO NOT spray water directly into the engine compartment or onto electrical components.

● Simulate electrical load

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

Connector Inspection Procedure

1. 1
   Connector Handling

   a.	Never pull on the wire harness when disconnecting connectors.

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

   b.	Listen for a click when connectors lock. This sound indicates that 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 wire.

2. 2
   Connector Checkpoints

   a.	With the connector connected: While holding the connector, check the connection condition and locking efficiency.

   b.	With the connector disconnected: Check for a missing terminal, crimped terminal or broken core wire by gently pulling the wire harness. Visually check for rust, contamination, deformation and bending.

   b.	Check terminal tightness: Insert a spare male terminal into the female terminal, then check the terminal tightness condition.

   d.	Gently pull on each individual wire to confirm that each wire is secured in the terminal.

3. 3
   Connector Terminal Repair Method

   a.	Clean the contact points using compressed air and/or a cloth. Never use sandpaper to polish contact points, as this may damage the contact point.

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

4. 4
   Before removing the wire harness, check the position and clamping of the wire harness to restore it correctly.
5. 5
   Check that the wire harness is not twisted, stretched or loose.
6. 6
   Check that the wire harness is not exposed to excessive temperature.
7. 7
   Check that the wire harness does not rotate, move or vibrate against sharp edges of components.
8. 8
   Check the connection between the wire harness and any installed part.
9. 9
   If the wire 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 wire harness up and down or from side to side.

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

    a.

    Disconnect connectors (A) and (C), then measure the resistance between connectors (A) and (C), as shown in [FIG. 2]. In [FIG. 2], the measured resistance of lines 1 and 2 is above 1 MΩ and below 1 Ω, respectively. Specifically, line 1 is open (line 2 is normal). To find the exact break point, inspect the sub-section of line 1 as described in the following step.

    b.

    Disconnect connector (B) and measure the resistance between connector (C) and (B1), and between (B2) and (A), as shown in [FIG. 3]. In this case, the measured resistance between connector (C) and (B1) is above 1 MΩ, indicating an open circuit 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 connector (A), (B) and (C), as shown in [FIG. 4]. The measured voltage of each connector is 5 V, 5 V and 0 V, respectively. Therefore, the circuit is open 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 breakpoint can be located by performing Step 2 (Continuity Check Method with chassis ground), as shown below.

    

14. 14
    Continuity Check Method (with Chassis Ground)

    When measuring resistance, gently shake the wire harness up and down or from side to side.

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

    a.

    Disconnect connectors (A) and (C), then measure the resistance between connector (A) and chassis ground, as shown in [FIG. 6]. In this example, the measured resistance of lines 1 and 2 is below 1 Ω and above 1 MΩ, respectively. Specifically, line 1 is shorted to ground (line 2 is normal). To find the exact fault location, inspect 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 Ω or less, indicating a short to ground between terminal 1 of connector (C) and terminal 1 of connector (B1).

Wire Harness Inspection Procedure: Electrical Circuit Inspection Procedure ● Check for open circuit ● Check for short circuit ● Voltage drop test. This test checks the voltage drop across a wire, connection, or switch.

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

B.	Connect the negative lead to the other end of the wire (or 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 difference or drop of more than 0.1 V (50 mV in a 5 V circuit) 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 Check the fuel pressure. (Refer to Fuel System - Repair Procedures - "Fuel Pressure Check") 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 Check the fuel pressure. (Refer to Fuel System - Repair Procedures - "Fuel Pressure Check") 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 Check the fuel pressure. (Refer to Fuel System - Repair Procedures - "Fuel Pressure Check") 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 Check the idle air control circuit (check DTC). 5 Inspect and check the throttle body 6 Check the ECT sensor and circuit (check DTC)	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 Check the fuel pressure. (Refer to Fuel System - Repair Procedures - "Fuel Pressure Check") 3 Check the idle air control circuit (check DTC). 4 Check the ignition circuit. (Refer to Engine Electrical System - "Ignition System") 5 Check the CKPS circuit (check DTC)	Trouble Code Intake air leaks Contaminated Fuel Weak ignition spark
Poor Driveability (Surging)	1 Check the fuel pressure. (Refer to Fuel System - Repair Procedures - "Fuel Pressure Check") 2 Inspect and check the throttle body 3 Check the ignition circuit. (Refer to Engine Electrical System - "Ignition System") 4 Check the ECT sensor and circuit (check DTC) 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. (See CUSTOMER DATA FLOW)	Trouble Code Low compression Intake air leaks Contaminated Fuel Weak ignition spark
Knock	1 Check the fuel pressure. (Refer to Fuel System - Repair Procedures - "Fuel Pressure Check") 2 Inspect the engine coolant. (Refer to Engine Mechanical System - "Radiator") 3 Inspect the radiator and electric cooling fan system. (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 air conditioner running continuously or is the defroster mode on? · Is the tire pressure correct? · Is the vehicle carrying an excessively heavy load? · Is the acceleration too strong or too frequent? 2 Check the fuel pressure. (Refer to Fuel System - Repair Procedures - "Fuel Pressure Check") 3 Check the injector. (Refer to Engine Control System - "Injector") 4 Check the exhaust system for possible blockage 5 Check the ECT sensor and circuit	Trouble Code Low compression Intake air leaks Contaminated Fuel Weak ignition spark
Hard to Refuel (Overflow during refueling)	1 Check the canister close valve. (Refer to Engine Control System - "Canister Close Valve") 2 Inspect the fuel tank hose/tube. · Pinched, kinked or blocked? · Torn filler hose 3 Inspect the fuel tank vapor hose between the EVAP canister and the air filter 4 Check the EVAP canister	Gas station fuel nozzle malfunction (If this problem occurs at a specific gas station during refueling)