Engine Controls - Tests W/o Codes: Other Lexus GS I

Engine Does Not Crank

1. Check starter.
2. Check starter relay.
3. Check Park/Neutral Position (PNP) switch circuit (clutch start switch circuit on SC300 M/T).
4. Check theft deterrent ECU.

No Initial Combustion

1. Check ECM power source circuit (ignition keyed).
2. Check ignition signal circuit. See SPARK TEST under IGNITION CHECKS in appropriate articles

For GS300 BASIC TESTING

For SC300 BASIC TESTING

For SC400 BASIC TESTING

1. Check fuel pump control circuit. See CODE 78 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check spark plugs.
2. Check fuel injector circuit.

No Complete Combustion

1. Check fuel pump control circuit. See CODE 78 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check ignition coil resistance.
2. Check distributor sensors.
3. Check spark plugs.
4. Check ignition signal circuit. See SPARK TEST under IGNITION CHECKS in appropriate articles

For GS300 BASIC TESTING

For SC300 BASIC TESTING

For SC400 BASIC TESTING

1. Check fuel injector circuit.

Difficult To Start Normally

1. Check starter signal circuit. See CODE 43 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Idle Air Control (IAC) valve circuit.
2. Check fuel pump control circuit. See CODE 78 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check ignition coil resistance.
2. Check distributor sensors.
3. Check spark plugs.
4. Check engine compression.
5. Check fuel injector circuit.

Difficult To Start When Cold

1. Check starter signal circuit. See CODE 43 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Idle Air Control (IAC) valve circuit.
2. Check fuel pump control circuit. See CODE 78 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check fuel injector circuit.
2. Check ignition coil resistance.
3. Check distributor sensors.
4. Check spark plugs.

Difficult To Start When Hot

1. Check starter signal circuit. See CODE 43 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Idle Air Control (IAC) valve circuit.
2. Check fuel pressure control VSV circuit (if equipped).
3. Check fuel pump control circuit. See CODE 78 in appropriate article

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check fuel injector circuit.
2. Check ignition coil resistance.
3. Check distributor sensors.
4. Check spark plugs.

Incorrect First Idle

1. Check switch condition signal circuit. See CODE 51 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Idle Air Control (IAC) valve circuit.

High Idle Speed

1. Check switch condition signal circuit. See CODE 51 in appropriate article

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Idle Air Control (IAC) valve circuit.
2. Check A/C signal circuit.
3. Check ECM power source circuit (ignition keyed).
4. Check Park/Neutral Position (PNP) switch circuit (clutch start switch circuit on SC300 M/T).
5. Check ECM back-up power circuit (battery).

Low Idle Speed

1. Check Idle Air Control (IAC) valve circuit.
2. Check A/C signal circuit.
3. Check switch condition signal circuit. See CODE 51 in appropriate article

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Park/Neutral Position (PNP) switch circuit (clutch start switch circuit on SC300 M/T).
2. Check fuel pump control circuit. See CODE 78 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check fuel injector circuit.
2. Check Volume Airflow (VAF) sensor circuit. See CODE 31 in appropriate article

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check ECM back-up power circuit (battery).

Rough Idle

1. Check switch condition signal circuit. See CODE 51 in appropriate article

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Idle Air Control (IAC) valve circuit.
2. Check Volume Airflow (VAF) sensor circuit. See CODE 31 in appropriate article

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check fuel injector circuit.
2. Check EGR system.
3. Check ignition signal circuit. See SPARK TEST under IGNITION CHECKS in appropriate articles

For GS300 BASIC TESTING

For SC300 BASIC TESTING

For SC400 BASIC TESTING

1. Check engine compression.
2. Check fuel pump control circuit. See CODE 78 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check ignition coil resistance.
2. Check distributor sensors.
3. Check spark plugs.

Surging

1. Check switch condition signal circuit. See CODE 51 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Idle Air Control (IAC) valve circuit.
2. Check Volume Airflow (VAF) sensor circuit. See CODE 31 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check ECM power source circuit (ignition keyed).
2. Check fuel pump control circuit. See CODE 78 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

Hesitation/Poor Acceleration

1. Check switch condition signal circuit. See CODE 51 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Volume Airflow (VAF) sensor circuit. See CODE 31 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check fuel injector circuit.
2. Check fuel pump control circuit. See CODE 78 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check ignition signal circuit. See SPARK TEST under IGNITION CHECKS in appropriate articles

For GS300 BASIC TESTING

For SC300 BASIC TESTING

For SC400 BASIC TESTING

1. Check ignition coil resistance.
2. Check distributor sensors.
3. Check spark plugs.
4. Check for faulty automatic transmission (electronics).

Muffler Explosion (Backfire)

1. Check switch condition signal circuit. See CODE 51 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check ignition coil resistance.
2. Check distributor sensors.
3. Check spark plugs.
4. Check fuel injector circuit.

1. Check switch condition signal circuit. See CODE 51 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check fuel pump control circuit. See CODE 78 in appropriate article

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check distributor sensors.
2. Check spark plugs.
3. Check fuel injector circuit.

Engine Stall After Start

1. Check fuel pump control circuit. See CODE 78 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Volume Airflow (VAF) sensor circuit. See CODE 31 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Idle Air Control (IAC) valve circuit.

Engine Stall After Accelerator Pedal Depressed

1. Check switch condition signal circuit. See CODE 51 in appropriate articles

For GS300 TESTS W/CODES

For SC300 TESTS W/CODES

For SC400 TESTS W/CODES

1. Check Volume Airflow (VAF) sensor circuit. See CODE 31 in appropriate articles

Engine Stall After Accelerator Pedal Released

1. Check fuel injector circuit.
2. Check Idle Air Control (IAC) valve circuit.
3. Check ECM ground circuits.

Engine Stall When Shifting From Neutral To Drive

1. Check Park/Neutral Position (PNP) switch circuit (clutch start switch circuit on SC300 M/T).
2. Check Idle Air Control (IAC) valve circuit.

Intermittent Simulation

Monitor circuit/component voltage or resistance while using the following procedures to simulate an intermittent fault. If engine is running, check for self-diagnostic codes. Use test results to identify a faulty component or circuit.

1. Lightly vibrate component.
2. Heat component.
3. Wiggle or bend wiring harness.
4. Spray component with water mist.
5. Remove vacuum from component.
6. Apply vacuum to component.