Engine Controls - System & Component Testing: Diagnosis Lexus GS II рестайлинг

Circuit Description

When ignition switch is turned on, 9-14 volts is applied to the terminal IGSW at ECM main relay control circuit. ECM then applies voltage to terminal MREL at ECM, switching EFI main relay on.

When engine is being cranked, intake airflow is slow, so fuel vaporization is poor. A rich mixture is necessary to achieve good startability. While engine is being cranked, 9-14 volts is supplied to ECM terminal STA. Starter signal is mainly used to increase fuel injection pulse for starting injection control and after-start injection control.

Note. The following test assumes starter cranks normally with ignition in START position. If starter does not crank normally, check and repair starter circuit before continuing with this test.

Diagnosis & Repair (Using Lexus Scan Tool)

1. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. (Scheme 36) Turn scan tool on. Turn ignition on. Using scan tool, read STA signal with ignition on and then while cranking starter.
2. With ignition on, STA signal should be off. With ignition switch in START position, STA signal should be on. If STA signal is not as specified, go to next step. If STA signal is as specified, no problem is indicated at this time. Diagnose by symptom. See «TROUBLE SHOOTING - NO CODES»(ref-134942) article.
3. Check for open in wiring harness between ECM and starter relay. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, replace ECM and retest.

Scheme 36

Diagnosis & Repair (Using OBD-II Scan Tool)

1. Access ECM at left front of engine compartment. Backprobing ECM connector, measure voltage between ground and following terminal: On GS300, terminal No. 2 (Black wire) at ECM connector E5. see scheme 6 On IS300, terminal No. 2 (Black wire) at ECM connector E4. see scheme 7 On GS430, terminal No. 12 (Black wire) at ECM connector E6. see scheme 8 On LS430, terminal No. 12 (Blue/Orange wire) at ECM connector E3. see scheme 9 On SC430, terminal No. 12 (White/Blue wire) at ECM connector E6. see scheme 9 On all models, go to next step.
2. Turn ignition switch to START position. With starter being cranked, voltage should be 6 volts or more. If voltage is not as specified, go to next step. If voltage is as specified, no problem is indicated at this time. Diagnose by symptom. See «TROUBLE SHOOTING - NO CODES»(ref-134942) article.
3. Check for open in wiring harness between ECM and starter relay. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, replace ECM and retest.

Testing EFI Main, Starter & Circuit Opening Relays

For relay terminal identification (Scheme 37)or (Scheme 38). If relay continuity is not as specified, replace relay and retest system.

1. Continuity should exist between terminals No. 1 and 2.
2. Continuity should not exist between terminals No. 3 and 5.
3. Apply battery voltage across terminals No. 1 and 2. Continuity should exist between terminals No. 3 and 5.

Scheme 37

Scheme 38

Testing Fuel Pump Relay (IS300, LS430 & SC430)

For relay terminal identification (Scheme 39) If relay continuity is not as specified, replace relay and retest system.

1. Continuity should exist between terminals No. 1 and 2.
2. Continuity should not exist between terminals No. 3 and 4.
3. Apply battery voltage across terminals No. 1 and 2. Continuity should exist between terminals No. 3 and 4.

Scheme 39

Fuel Pump Control Circuit - IS300, LS430 & SC430 (Using Lexus Scan Tool)

1. Connect Lexus scan tool to DLC3. (Scheme 36) Check fuel pump system operation. See «FUEL PUMP OPERATION»(ref-134934-S36940904812002022100000) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel pump operates, go to step 8. If fuel pump does not operate, go to next step.
2. Using Lexus scan tool, select ACTIVE TEST mode. Locate fuel pump relay in underhood relay block mounted in front of driver's side strut tower. Listen for noise while activating fuel pump relay. If relay noise can be heard when activated, go to step 4. If relay can not be heard when activated, go to next step.
3. Check operation of fuel pump relay. See «TESTING FUEL PUMP RELAY (IS300, LS430 & SC430)»(ref-134943-S20094489032002022100000) under RELAYS under MOTORS, RELAYS & SOLENOIDS. Replace relay as necessary. If fuel pump relay is okay, go to next step.
4. Check for faulty fuel pump. See «FUEL PUMP RESISTANCE»(ref-134943-S04532405802002022100000) and «FUEL PUMP OPERATION (USING BATTERY VOLTAGE)»(ref-134943-S14866477542002022100000). Replace fuel pump as necessary. If fuel pump is okay, go to next step.
5. Check operation of circuit opening relay. See «TESTING EFI MAIN, STARTER & CIRCUIT OPENING RELAYS»(ref-134943-S01037480482002022100000) under RELAYS under MOTORS, RELAYS & SOLENOIDS. Replace relay as necessary. If circuit opening relay is okay, go to next step.
6. Check for open circuit in wiring or connectors between EFI main relay, circuit opening relay and ECM, between circuit opening relay and fuel pump relay, and between fuel pump relay and fuel pump. Also check for open circuit between fuel pump and ground. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If no problem is found, go to next step.
7. Access ECM at left front of engine compartment. Turn ignition on. Measure voltage between ground and following ECM terminal: On IS300, terminal No. 5 (Green/Yellow wire) at ECM connector E3. see scheme 7 On LS430, terminal No. 14 (Green/Black wire) at ECM connector E3. see scheme 9 On SC430, terminal No. 14 (Green/Black wire) at ECM connector E6. see scheme 8 If voltage is 9-14 volts, no problem is indicated at this time. If voltage is not 9-14 volts, locate and repair open circuit between battery and ECM terminal listed. See «WIRING DIAGRAMS»(ref-134952) article.
8. Locate fuel pump resistor under protective cover on driver's strut tower in engine compartment. Disconnect fuel pump resistor Black 2-pin connector. Measure resistance between resistor terminals. If resistance is not.30-.35 ohm at 68°F (20°C), replace resistor. If resistance is.30-.35 ohm, check for open circuit between fuel pump relay and fuel pump resistor, or fuel pump resistor and fuel pump. Repair as necessary. See «WIRING DIAGRAMS»(ref-134952) article. If wiring is okay, replace ECM and retest.

Fuel Pump Control Circuit - IS300, LS430 & SC430 (Using OBD-II Scan Tool)

1. Connect Lexus scan tool to DLC3. (Scheme 36) Check fuel pump system operation. See «FUEL PUMP OPERATION»(ref-134934-S36940904812002022100000) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel pump operates, go to step 7. If fuel pump does not operate, go to next step.
2. Check operation of fuel pump relay. See «TESTING FUEL PUMP RELAY (IS300, LS430 & SC430)»(ref-134943-S20094489032002022100000) under RELAYS under MOTORS, RELAYS & SOLENOIDS. Replace relay as necessary. If fuel pump relay is okay, go to next step.
3. Check for faulty fuel pump. See «FUEL PUMP RESISTANCE»(ref-134943-S04532405802002022100000) and «FUEL PUMP OPERATION (USING BATTERY VOLTAGE)»(ref-134943-S14866477542002022100000). Replace fuel pump as necessary. If fuel pump is okay, go to next step.
4. Check operation of circuit opening relay. See «TESTING EFI MAIN, STARTER & CIRCUIT OPENING RELAYS»(ref-134943-S01037480482002022100000) under RELAYS under MOTORS, RELAYS & SOLENOIDS. Replace relay as necessary. If circuit opening relay is okay, go to next step.
5. Check for open circuit in wiring or connectors between EFI main relay, circuit opening relay and ECM, between circuit opening relay and fuel pump relay, and between fuel pump relay and fuel pump. Also check for open circuit between fuel pump and ground. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If no problem is found, go to next step.
6. Access ECM at left front of engine compartment. Turn ignition on. Measure voltage between ground and following ECM terminal: On IS300, terminal No. 5 (Green/Yellow wire) at ECM connector E3. see scheme 7 On LS430, terminal No. 14 (Green/Black wire) at ECM connector E3. see scheme 9 If voltage is 9-14 volts, no problem is indicated at this time. If voltage is not 9-14 volts, locate and repair open circuit between battery and ECM terminal listed. See «WIRING DIAGRAMS»(ref-134952) article.
7. Locate fuel pump resistor under protective cover on driver's strut tower in engine compartment. Disconnect fuel pump resistor Black 2-pin connector. Measure resistance between resistor terminals. If resistance is not.30-.35 ohm at 68°F (20°C), replace resistor. If resistance is.30-.35 ohm, check for open circuit between fuel pump relay and fuel pump resistor, or fuel pump resistor and fuel pump. See «WIRING DIAGRAMS»(ref-134952) article. Repair as necessary. If wiring is okay, replace ECM and retest.