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Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 Chevrolet Suburban, and 2002 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the diagnostic system check? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Install a scan tool. Turn ignition on, engine off. Before clearing the DTCs, use the scan tool to record the failure records. Using the CLEAR INFO function erases the failure records from the PCM. Record the failure records. Clear the DTCs. Select STOPLAMP SWITCH on the scan tool. Do not apply the brake pedal. With the brake pedal not applied, note the stoplamp switch status. Apply the brake pedal. Did the stoplamp switch status change from CLOSED to OPEN? If so, see DIAGNOSTIC AIDS . If not, go to next step.
  3. Turn ignition off. Disconnect the stoplamp switch connector from the switch. Turn ignition on, engine off. Did the stoplamp switch status change from CLOSED to OPEN? If so, go to next step. If not, go to step  5.
  4. Replace the stoplamp switch. See STOPLAMP SWITCH  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  7.
    5. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
  5. Test the brake switch signal circuit (420) for a short to voltage. Did you find and correct the condition? If so, go to step  7. If not, go to next step.
  6. Replace the PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
  7. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Operate the brake pedal so that for a total of 2 consecutive times the PCM sees the stoplamp switch CLOSED and then OPEN, for greater than 2 seconds.

    Does the stoplamp switch status change from CLOSED to OPEN? If so, system is okay. If not, go to step  1.

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