Fault Diagnosis, Input From Brake Light Switch

FAULT DIAGNOSIS, INPUT FROM BRAKE LIGHT SWITCH

Symptom of fault
Full boost pressure even when the brake pedal is activated

Diagnostic procedure
1. Connect an ISAT scan tool.

- Ignition switched ON.
- Select "BRAKE LIGHT SWITCH" in the ISAT menu "READ ON/OFF".
- Check the brake light switch by depressing and releasing the brake pedal.
- If the ISAT shows the correct value, continue at "Procedure before replacing ECM".
- If the ISAT shows an incorrect value, check that the brake light works when the pedal is depressed.
- If the brake light works, the fault is located in the lead between pin 15 of the ECM and crimped connection J67.
- If the brake light does not work, continue fault diagnosis in the electrical system.