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Troubleshooting Tips

OUTLINE




Main Relay (Battery Power)
- If the circuit is open, the engine will not start.
- If the circuit is shorted, the EGI INJ fuse (40 A) will burn out.




Room Fuse (ECM Memory Power)
- If the circuit is open, the ECM memory function will not operate, and diagnostic trouble codes for intermittent malfunctions will not be indicated. Also, the learning control will be canceled, but will not produce any particular symptom.
- If the circuit is shorted, the ROOM fuse (15 A) will burn out.




Ground (Output Devices, Fuel Injector)
- If an output device or a fuel injector has an open ground circuit, no particular symptom will be produced.
- If a related output device and injectors both have open ground circuits, the engine will not start.

Ground (System, Analogue)
- An open circuit will not produce any symptom.




Terminal TEN (Data Link Connector)
- If the circuit is shorted, the opening amount of the idle air control valve will not change, causing hard starting and rough idle. The ignition timing will be fixed, causing lack of power and poor acceleration.
- If the circuit is shorted, the coolant fan operates whenever the throttle valve is opened (Ignition switch ON).




Terminal KLN (Data Link Connector 2)
- If both circuits are open or short, the NGS indicates "LINK COMMUNICATION ERROR".




Serial Line
- If each or both lines have an open or short, Diagnostic trouble Code No.P1 601 is output.

INPUT DEVICES




Mass Air Flow Sensor
- If the Vs terminal of the mass air flow sensor has a short circuit, Diagnostic Trouble Code No.0100 will be output, and the throttle position sensor and closed throttle position switch signal will be used to adjust the basic injection amount as to the following three modes.
1) Closed throttle position switch ON
2) Small throttle angle
3) Large throttle angle




Throttle Position Sensor
- If the VREF terminal has an open circuit or the TVO terminal has an open or short circuit, Diagnostic Trouble Code No.P0120 is output.
- If the VREF terminal has an short circuit, the engine will not start or laugh idle.
- If the ground terminal has an open circuit, Diagnostic Trouble Code No.P0120 is output.
- In the above conditions, the ECM uses a throttle valve fully-open program.
- If the throttle position sensor is not properly adjusted or the throttle position sensor system fails, poor acceleration or shift shock will result.




Intake Air Temperature Sensor (A/C)
- If the thermosensor or circuit has an open or short, Diagnostic
- Trouble Code No.P0110 is output, and the ECM uses a preprogrammed intake air temperature of -10°C (14°F).
- If the intake air temperature sensor system fails, no particular symptom will be noticed.

Closed Throttle Position Switch (In Throttle Position Sensor)
- If the circuit is open, rough idle or engine stalling may appear because of inoperative idle air control.
- If the circuit is shorted, fuel will be cut when the accelerator pedal is pressed, causing hunting.




Heated Oxygen Sensor
- If sensor signal "lean" for approximately 2 minutes in feedback zone, Diagnostic Trouble Code No.P0154, P0160 (left bank sensor) and/or P0134, P0140 (right bank sensor) is output.
- If the heated oxygen sensor signal remain unchanged for approximately 40 seconds in feedback zone, Diagnostic Trouble Codes No.P0150 (left bank sensor) and/or P0130 (right bank sensor) is output.
- In the above conditions, no feedback control will be present and no symptom will be noticed.







Crankshaft Position Sensor (NE Signal), Camshaft Position Sensor (SGC Signal)
- If the NE signal circuit has an open or short, Diagnostic Trouble Code No.P0335 is output.
- If the SGC signal circuit has an open or short, Diagnostic Trouble Code No.P1345 is output.

Starter Signal
- A lack of starter signal input will cause hard starting.




P/S Pressure Switch
- An open circuit can cause a momentary drop in engine speed when steering at idle or low-speed driving.




A/C Signal (A/C Amplifier)
- If the circuit is open, the air conditioner will not operate.
- If the circuit is shorted, the air conditioner will constantly operate when the blower is ON.




Engine Coolant Temperature Sensor
- If the thermosensor or circuit has an open or short, Diagnostic Trouble Code No.P0115 output, and the ECM uses a preprogrammed temperature value of 52°C (125.60 F) and coolant fan and condenser fan operate continuously.
- A malfunction in the engine coolant temperature sensor system may cause rough idle, engine stalling, or hard starting.




Blower Signal (A/C Amplifier)
- If the circuit has an open, the idle speed may drop when in the high position.




Brake Signal
- An open or short circuit will produce no symptom.

High Air Charging Pressure Control Signal
- If the circuit is open, torque reduction control will not operate.
- If the circuit is shorted, always operates torque reduction control, causing poor acceleration or lack of power.




Vehicle Speed Sensor
- If the sensor or circuit has an open or short, diagnostic trouble code No.P0500 is output.
- If the circuit is open or shorted, no symptom will be noticed.




Manifold Absolute Pressure Sensor
- If the sensor or circuit has an open or short circuit, diagnostic trouble code No. P0105 is output, and the ECM uses a preprogrammed manifold pressure of 101 kPa (760 mmHg).
- A malfunction in the MAP system may cause poor acceleration or lack of power.




Intake Air Temperature Sensor (DIC)
- If the sensor or circuit has an open or short, diagnostic trouble code No.Pi1iO is output and the ECM uses a preprogrammed intake air temperature of 60°C (140°F)
- A malfunction in the intake air temperature sensor, no symptom will be noticed.




Intake Air Temperature Sensor (LIC)
- If the sensor or circuit has an open or short, diagnostic trouble code No.P1113 is output, and the ECM uses a preprogrammed intake air temperature of 60°C (140°F).
- A malfunction in the intake air temperature sensor (LIC), no symptom will be noticed.







Torque Reduction Request Signal (ABS/TCS Control Unit)
- If a malfunction occurs in the torque reduction request signal, the traction control (TCS) is inhibited and TCS does not operate.




Knock Sensor
- If the knock sensor or circuit has an open or short, Diagnostic Trouble Code No.P0325 is output.
- In the above conditions, ignition timing is retarded, causing poor acceleration or lack of power.




EGR Valve Position Sensor
- If the EGR valve position sensor or circuit has an open or short, Diagnostic Trouble Code No.P14O2 is output.
- In the above conditions, the EGR valve will be fully closed.




Rear Window Defroster Signal (A/C Amplifier)
- An open circuit can cause a low idle speed.
- An short circuit can cause a slightly high idle speed.




Headlight Switch
- An open circuit can cause a low idle speed.
- An short circuit can cause a slightly high idle speed.

OUTPUT DEVICES




Fuel Injector
- If the circuit is open, the fuel injector will not operate, causing rough idle and misfiring.
- If the circuit is shorted, the fuel injector will inject fuel constantly, will not start or hard start.




IGT Signal (Ignition coil)
- If no IGT signal(s) are input to the ignition coil because of an open or short circuit, the cylinder(s) will not start.




Idle Air Control Valve (IAC Valve)
- If the solenoid valve or circuit has an open or short, Diagnostic Trouble Code No.P05O5 is output.
- If the circuit is open, the solenoid valve will be fully closed, causing rough idle, engine stalling, and acceleration hesitation when cold.
- If the circuit is shorted, the idle air control valve will be fully opened and the idle speed will be increased, causing hunting.




Fuel Pump Relay
- If the circuit is open, the engine will not start.
- If the circuit is shorted, the fuel pump will operate whenever the ignition switch is ON.




Purge Solenoid Valve
- If the solenoid valve or circuit has an open or short, Diagnostic Trouble Code No.P0443 is output.
- If the circuit is open, no symptom will be noticed.
- If the circuit is shorted, the engine stall or laugh at low speed.
- A short circuit may cause an improper air/fuel ratio, causing rough idle and hard starting.




A/C Signal (A/C Relay)
- If the circuit is open, the air conditioner will not operate.
- if the circuit is shorted, the air conditioner will constantly operate when ignition switch ON.




Torque Reduction Inhibit Signal (ABS/TCS Control Unit)
- If the circuit is open or shorted, the traction control will not operate.




EGR Solenoid Valve (Vent)
- If the solenoid valve or circuit has an open or short, Diagnostic Trouble Code No.P1486 is output.
- If the circuit is open or shorted, no symptom will be noticed.




EGR Solenoid Valve (Vacuum)
- If the solenoid valve or circuit has an open or short, Diagnostic Trouble Code No.P1485 is output.
- If the circuit is shorted, the EGR valve will remain open, causing engine stalling and hard starting.
- If the circuit is open, no symptom will be noticed.




PRC Solenoid Valve
- If the solenoid valve or circuit has an open or short, Diagnostic Trouble Code No.P1250 is output.
- If the circuit is shorted, no symptom will be noticed.
- If the circuit is open, the engine will be hard to start when hot.




Condenser Fan Relay No.1
- If the circuit is shorted, the condenser fan and coolant fan will always operate while the ignition switch is ON.
- If the circuit is open, the condenser fan will not operate.




Cooling Fan Relay No.1 and Condenser Fan Relay No.2
- If the circuit is shorted, the cooling fan and condenser fan will always operate while the ignition switch is ON.
- If the circuit is open, the cooling fan will remain OFF when the engine temperature exceeds 108°C (226°F).







ABV Solenoid Valve (Vacuum)
- If the solenoid valve or circuit has an open or short, diagnostic trouble code No.P1525 is output.
- If the circuit is open, no symptom will be noticed.
- If the circuit is shorted, the ABV actuator is not controlled causing poor acceleration or lack of power.




ABV Solenoid Valve (Vent)
- If the solenoid valve or circuit has an open or short, diagnostic trouble code No.P1 526 is output.
- If the circuit is open, no symptom will be noticed.
- If the circuit is shorted, the ABV actuator is not controlled causing poor acceleration or lack of power.




Charge Air Cooler Bypass Solenoid Valve
- If the solenoid valve or circuit has an open or short, diagnostic trouble code No.P1524 is output.
- If the circuit is open, no symptom will be noticed.
- If the circuit is shorted, the charge air cooler bypass valve always closed, the air charging pressure control is not controlled causing poor acceleration, lack of power or knocking.




MAP Sensor Solenoid Valve
- If the solenoid valve or circuit has an open or short, diagnostic trouble code No.P1487 is output.
- If the circuit is open, ECM can not detect the manifold pressure, causing poor acceleration or lack of power.
- If the circuit is shorted, no symptom will be noticed.




Bypass Air Solenoid Valve No.1
- If the solenoid valve or circuit has an open or short, diagnostic trouble code No.P1 508 is output.
- If the circuit is open, lack of air amount for starting when engine is very cold, causing hard to start.
- If the circuit is shorted, high idle speed after warm-up.

Bypass Air Solenoid Valve No.2
- If the circuit is open, lack of air amount for starting when engine is very cold, causing hard to start.
- If the circuit is shorted, high idle speed after warm-up.




Fuel Pump Resistor and Relay (Speed)
- If the circuit is shorted, the fuel pump does not operate at high speed causing poor acceleration or lack of power when heavy duty driving.
- If the circuit is open, fuel pump does not operate, causing engine will not start.




Cooling Fan Relay No.2 and No.3
- If the circuit is shorted, the cooling fan will always operate while the ignition switch ON.
- If the circuit is open, the cooling fan will remain OFF when water temperature exceeds 108°C (226°F).




High Air Charging Pressure Zone Signal
- If the circuit is open, torque reduction control will not operate.
- If the circuit is shorted, always operates torque reduction control, causing poor acceleration or lack of power.

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