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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 85 (Engine Controls - Self-Diagnostics - 8.1L) >> Diagnostic Tests >> DTC P0724: Brake Switch Circuit - High Input (4L80-E A/T) >> Diagnostic Procedures

Diagnostic Procedures

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  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. CAUTION: When you are performing service on or near the SIR components or the SIR wiring, you must disable the SIR system. See appropriate AIR BAG RESTRAINT SYSTEMS article in ACCESSORIES & EQUIPMENT. Failure to follow the correct procedure could cause air bag deployment, personal injury, or unnecessary SIR system repairs.
    NOTE: Before clearing the DTCs, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
  2. Install a scan tool. Turn ON the ignition, with the engine OFF. Record the Failure Records. Clear the DTCs. Select TCC Brake Switch on the scan tool. Do not apply the brake pedal. With the brake pedal not applied, note the TCC brake switch status. Apply the brake pedal. Did the TCC Brake Switch status change from CLOSED to OPEN? If yes, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to next step.
  3. Turn OFF the ignition. Disconnect the TCC/Stoplamp switch connector from the brake switch. Turn ON the ignition, with the engine OFF. Did the TCC Brake Switch status change from CLOSED to OPEN? If yes, go to next step. If no, go to step  5.
  4. Replace the stoplamp switch. See ADJUSTMENTS in appropriate DISC & DRUM article in BRAKES. After repairs, go to step  7.
    5. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
  5. Test the TCC brake switch signal circuit (CKT 420) for a short to voltage. Did you find and correct the condition? If yes, go to step  7. If no, go to next step.
  6. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  7. Perform the following procedure in order to verify the repair:
    • Select DTC.
    • Select Clear Info.
    • Apply the brake pedal several times. Ensure the scan tool Brake Switch displays OPEN when the pedal is applied and CLOSED when the pedal is released.

    Does the scan tool TCC Brake Switch status change from CLOSED to OPEN? If yes, system is okay. If no, go to step  1.

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