Stoplight Switch Circuit Problem: Description
When brake pedal is depressed, stoplight switch completes circuit, and battery voltage is sent to ECM. When ECM receives stoplight switch signal, ECM cancels cruise control. Another part of stoplight switch is normally closed, allowing battery voltage to reach ECM. When brake pedal is depressed, switch opens circuit. If first stoplight switch circuit is open, ECM will sense a problem. Cruise control will be shut off and a code stored.
NOTE:
If LEXUS hand held tester is not available, start test at step 2.
- Connect LEXUS hand-held tester to Data Link Connector 3 (DLC3), located under left side of instrument panel. Select DATALIST on tester. Check stoplight switch "1" input to ECM. Check stoplight switch "2" input to ECM. Stoplight switch input display should be off when brake pedal is released, and on when pedal is depressed. If stoplight switch input display is not as specified, go to next step. If stoplight switch input display is okay, perform next procedure listed in DIAGNOSIS BY SYMPTOM table under TROUBLE SHOOTING.
- Check stoplight switch. With switch pin released, continuity should exist between terminals No. 1 and No. 2. Continuity should not exist between terminals No. 3 and No. 4. See Fig 1. With switch pin pressed, continuity not should exist between terminals No. 1 and No. 2. Continuity should exist between terminals No. 3 and No. 4. Replace as necessary. If switch is okay, go to next step.
- Check for faulty circuits between ECM and stoplight switch. See WIRING DIAGRAMS . Repair circuit(s) if necessary. If circuits are okay, replace ECM.