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.
NOTE:
If not using the hand-held tester, start the inspection from step 2.
- Check the stop light switch using the hand-held tester. Connect the hand-held tester to the DLC3. Check that the stop light switch using DATA LIST. See STOP LIGHT SWITCH DATA LIST table.STOP LIGHT SWITCH DATA LIST
Stop Light Switch 1 (Sub CPU) Stop Light Switch 2 (Sub CPU) Stop Light Switch 2 (Main CPU) Depressed ON ON ON Released OFF OFF OFF - Stop light SW 1 has a function to disconnect the connection (OFF) when depressing the pedal, however, ECM controls by the logic reverse, so with the hand-held tester, it displays ON.
- Stop light SW 1 indicates the input of E6-8 (ST1-) terminal and stop light SW 2 indicates the input of STP terminal. See Fig 2
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 that the stop light comes on when the brake pedal is depressed, and turns off when the brake pedal is released. If the results are OK, go to the next step. If the results are not OK, see stop light system. See appropriate BODY CONTROL SYSTEMS article in COMMUNICATION DEVICES.
- Remove the ECM with connectors still connected. Turn the ignition switch ON. Measure the voltage between terminal E5-4 (STP) 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.MEASURING ECM TERMINAL E5-4 & E6-8 VOLTAGE
Brake Pedal Voltage Depressed 10-14 Released Less Than 1 - Check the wire harness and connector between terminal E5-4 (STP) of the ECM and the stop light switch, and terminal E6-8 (ST1-) of the ECM and the stop light switch. If the results are OK, check and replace the ECM. If the results are not OK, repair or replace the harness or connector.