Test A: Stoplight Switch Circuitry
- Check Stoplight Operation - Press and hold brake pedal to check stoplight operation. If stoplights operate properly, go to next step. If stoplights do not operate properly, see appropriate EXTERIOR LIGHTS wiring diagram in SYSTEM WIRING DIAGRAMS article in the WIRING DIAGRAMS section to continue diagnosis.
- Check Stoplight Switch Input - Disconnect speed control servo/actuator connector C116 (located on left side of engine compartment). Press and hold brake pedal. Using a voltmeter, check voltage between ground and speed control servo/actuator connector C116 terminal No. 4 (Red/Light Green wire). See Fig 1 . If battery voltage is not present, go to next step. If battery voltage is present, go to step 4).
- Check Red/Light Green Wire For Open - Disconnect Brake On/Off (BOO) switch connector C251 (located on top of brake pedal assembly). Using an ohmmeter, check resistance in Red/Light Green wire between BOO switch connector C251 and speed control servo/actuator connector C116 terminal No. 4. If resistance is less than 5 ohms, replace speed control servo/actuator. Repeat SELF-DIAGNOSTIC TEST under SELF-DIAGNOSTIC SYSTEM. Test drive vehicle to check operation. If resistance is 5 ohms or more, repair open in Red/Light Green wire. Repeat SELF-DIAGNOSTIC TEST under SELF-DIAGNOSTIC SYSTEM. Test drive vehicle to check operation.
- Check Red/Light Green Wire For Short To Voltage - Ensure brake pedal is released. Using a voltmeter, check voltage between ground and speed control servo/actuator connector C116 terminal No. 4. See Fig 1 . If battery voltage is present, repair Red/Light Green wire for short to voltage. Repeat SELF-DIAGNOSTIC TEST under SELF-DIAGNOSTIC SYSTEM. Test drive vehicle to check operation. If battery voltage is not present, replace speed control servo/actuator. Repeat SELF-DIAGNOSTIC TEST under SELF-DIAGNOSTIC SYSTEM. Test drive vehicle to check operation.