Test 1: Stoplight Switch Circuit
WARNING: This page is about a different car, the 1997 Lexus SC 400. However, it is still accessible from the selected car via links, so may be relevant.
- If stoplights do not operate, repair stoplight circuit. If stoplights operate, check stoplight switch input signal circuit. See INPUT SIGNAL CIRCUITS . If input signal circuit is okay, perform next procedure listed in DIAGNOSIS BY SYMPTOM table under TROUBLE SHOOTING.
- If input signal circuit is faulty, remove cruise control ECU, but leave electrical connectors attached. Turn ignition on. Measure voltage between ground and terminals No. 1 and 16 of cruise control ECU connector. See Figure. With brake pedal pressed, battery voltage should be present at both terminals. With brake pedal released, battery voltage should be present at terminal No. 1, and less than one volt should be present at terminal No. 16.
- If voltage is as specified, perform next procedure listed in DIAGNOSIS BY SYMPTOM table under TROUBLE SHOOTING. If voltage is not as specified, check for faulty circuits between cruise control ECU and stoplight switch. Repair circuit(s) if necessary. If circuits are okay, replace cruise control ECU.