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Stoplight Switch Circuit

  1. Check stoplight operation. 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 not okay, go to next step. If input signal circuit is okay, perform next procedure listed in SYMPTOM DIAGNOSIS  table under TROUBLE SHOOTING.
  2. Remove cruise control ECU, leaving electrical connector attached. Turn ignition on. Measure voltage (backprobe) between cruise control ECU connector terminal No. 2 and ground while pressing and releasing brake pedal. See Figure. With brake pedal pressed, voltage should be 10-14 volts. With brake pedal released, voltage should be less than one volt. If voltage is not as specified, go to next step. If voltage is as specified, perform next procedure listed in SYMPTOM DIAGNOSIS  table under TROUBLE SHOOTING.
  3. Check wiring and connectors between cruise control ECU and stoplight switch. Repair or replace as necessary. If wiring and connectors are okay, check cruise control ECU. See CRUISE CONTROL ECU PIN VOLTAGE TESTS  under COMPONENT TESTS. If cruise control ECU is defective, replace ECU.
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