Diagnostic Procedure
WARNING: This page is about a different car, the 2002 Lexus GS 430 and 2002 Lexus GS 300. However, it is still accessible from the selected car via links, so may be relevant.
For circuit wiring diagram, see Fig 1.
- Check the voltage between terminal E6-8 (ST1-) of the ECM connector and body ground, when the brake pedal is depressed and released. See MEASURING ECM TERMINAL E5-4 & E6-8 VOLTAGE table. If the results are OK, perform the next test procedure of the problem symptom. See PROBLEM SYMPTOM INDEX table. If the results are not OK, go to the next step.
- Check for an open in the harness or connectors between terminal E6-8 (ST1-) of the ECM and the stop light switch. See Figure. If the results are OK, go to the next step. If the results are not OK, repair or replace the harness or connector.
- Remove the ECM with the connector still connected. Turn the ignition switch ON. Measure the voltage between terminals E5-31 (CCS) of the ECM connector and body ground, when each of the SET/COAST, RESUME/ACCEL and CANCEL is turned ON. See MEASURING ECM TERMINAL E5-31 VOLTAGE table. If the results are OK, go to the next step. If the results are not OK, perform the next test procedure of the problem symptom. See PROBLEM SYMPTOM INDEX table.MEASURING ECM TERMINAL E5-31 VOLTAGE
Switch Position Volts Neutral 10-16 RES/ACC 2.4-3.8 SET/COAST 4.7-6.9 CANCEL 6.9-9.8 - Check the control switch continuity. Remove the steering wheel pad. See WHEEL PAD & STEERING WHEEL under REMOVAL & INSTALLATION in appropriate STEERING COLUMN SWITCHES article. Disconnect the control switch connector. Measure the resistance between terminal Nos. 4 and 5 of the control switch connector when the control switch is operated. See Fig 2. See MEASURING CRUISE CONTROL SWITCH TERMINAL NOS. 4 & 5 RESISTANCE table. If the results are OK, go to the next step. If the results are not OK, replace the control switch. See CRUISE CONTROL SWITCH under REMOVAL & INSTALLATION.MEASURING CRUISE CONTROL SWITCH TERMINAL NOS. 4 & 5 RESISTANCE
Switch Position Resistance (Ohms) Neutral Infinity (No Continuity) RES/ACC 220-260 SET/COAST 600-660 CANCEL 1500-1600 - Check the main switch continuity. Remove the steering wheel pad. See WHEEL PAD & STEERING WHEEL under REMOVAL & INSTALLATION in appropriate STEERING COLUMN SWITCHES article. Disconnect the control switch connector. Check the continuity between terminal Nos. 4 and 5 of the control switch connector when the main switch is held ON and OFF. See CHECKING CRUISE CONTROL SWITCH TERMINAL NOS. 4 & 5 CONTINUITY table. If the results are OK, go to the next step. If the results are not OK, replace the control switch. See CRUISE CONTROL SWITCH under REMOVAL & INSTALLATION.CHECKING CRUISE CONTROL SWITCH TERMINAL NOS. 4 & 5 CONTINUITY
Switch Position Tester Connection Specified Condition OFF ..... No Continuity Hold ON 4 - 5 Continuity - Check the harness and connector between the ECM and cruise control switch, cruise control switch and body ground. If the results are OK, go to the next step. If the results are not OK, repair or replace the harness or connector.
- Check the cruise control indicator light. See COMBINATION METER CIRCUIT PLATE under CIRCUIT TESTS in appropriate INSTRUMENT PANEL article. If the results are OK, check and replace the ECM. If the results are not OK, replace the combination meter. See COMBINATION METER under REMOVAL & INSTALLATION in appropriate INSTRUMENT PANEL article.