Engine Controls - Trouble Shooting - No Codes: Other Lexus SC II

DOES NOT START

Engine Does Not Crank

1. Check battery and battery cables.
2. Check starter.
3. Check starter relay. See appropriate SYSTEM & COMPONENT TESTING article.

No Initial Combustion

1. Check engine immobilizer system. See appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT.
2. Check ECM power source circuit with ignition on. See ECM POWER SOURCE CIRCUIT (IGNITION KEYED) under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.
3. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.
4. Check Electronic Control Module (ECM) connector for loose, damaged or corroded terminals and repair as necessary. If connector is okay, check ECM ground circuits. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If ground circuits are okay, replace ECM with a known-good ECM and retest.

No Complete Combustion

1. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.

DIFFICULT TO START

Difficult To Start, Cranks Normal

1. Check starter signal circuit. See STARTER SIGNAL CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article. For GX470 and LX470 see DTC P0617 in appropriate SELF-DIAGNOSTICS article.
2. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.
3. Check engine compression. See «BASIC DIAGNOSTIC PROCEDURES»(ref-151770) article.

Difficult To Start When Cold

1. Check starter signal circuit. See STARTER SIGNAL CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article. For GX470 and LX470 see DTC P0617 in appropriate SELF-DIAGNOSTICS article.
2. Check fuel pump control circuit. On all models , see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.

Difficult To Start When Hot

1. Check starter signal circuit. See STARTER SIGNAL CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article. For GX470 and LX470 see DTC P0617 in appropriate SELF-DIAGNOSTICS article.
2. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.

POOR IDLING

High Idle Speed

1. Check A/C compressor signal circuit. See appropriate AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
2. Check ECM power source circuit with ignition on. See ECM POWER SOURCE CIRCUIT (IGNITION KEYED) under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.

Low Idle Speed

1. Check A/C compressor signal circuit. See appropriate AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
2. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.

Rough Idle

1. Check engine compression. See «BASIC DIAGNOSTIC PROCEDURES»(ref-151770) article.
2. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.

Surging

1. Check ECM power source circuit with ignition on. See ECM POWER SOURCE CIRCUIT (IGNITION KEYED) under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article.
2. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.

POOR DRIVEABILITY

Hesitation/Poor Acceleration

1. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.
2. Check for faulty automatic transmission (electronics). See appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS.

Surging

1. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.

ENGINE STALL

Engine Stall After Start

1. Check engine immobilizer system. See appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT.
2. Check fuel pump control circuit. On all models, see FUEL PUMP CONTROL CIRCUIT under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.

Engine Stall During A/C Operation

1. Check A/C compressor signal circuit. See appropriate AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
2. Check Electronic Control Module (ECM) connector for loose, damaged or corroded terminals and repair as necessary. If connector is okay, check ECM ground circuits. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If ground circuits are okay, replace ECM with a known-good ECM and retest.

Unable To Refuel Or Difficult To Refuel

1. Check fuel Evaporation (EVAP) system. See FUEL EVAP SYSTEM TEST under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the following methods

1. Lightly vibrate component. See «VIBRATION METHOD»(ref-151782-S22806558652003010800000) .
2. Heat component. See «HEATING METHOD»(ref-151782-S14840664172003010800000) .
3. Wiggle or bend wiring harness. See «VIBRATION METHOD»(ref-151782-S22806558652003010800000) .
4. Spray component with water. See «WATER SPRINKLING METHOD»(ref-151782-S31341838302003010800000) .
5. Remove vacuum from component.
6. Apply vacuum to component. Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for Diagnostic Trouble Codes (DTCs). Use test results to identify a faulty component or circuit.
7. If malfunction seems to occur when electrical load is high, turn on all electrical equipment including heater blower, headlights, rear window defogger, etc. and check of malfunction occurs.

WATER SPRINKLING METHOD

Spray outside of vehicle and front of radiator with water while checking for a malfunction to exist. DO NOT spray water directly into engine compartment. The temperature and humidity may be changed by spraying water onto the front of the radiator. DO NOT directly spray electronic components with water.