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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 81 (Engine Controls - Self-Diagnostics - 8.1L) >> Diagnostic Tests >> DTC P0719: Brake Switch Circuit - Low 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 the TCC Brake Switch on the scan tool. Do not apply the brake pedal. Does the scan tool TCC/Brake Switch indicate CLOSED, when the brake pedal is not applied? If yes, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to next step.
  3. Remove the brake fuse. Inspect the brake fuse for an open. Is the fuse open? If yes, go to step  10. If no, go to next step.
  4. Turn OFF the ignition. Disconnect the PCM connector C1 from the PCM. Connect a 12-volt test lamp to a good ground. Using the J 35616-A connector test adapter kit and the 12-volt test lamp, probe terminal C1-33. Re-install the fuse. Turn ON the ignition, with the engine OFF. Do not apply the brake pedal. Does the test lamp illuminate? If yes, go to step  15. If no, go to next step.
  5. Turn OFF the ignition. Remove the connector from the TCC/Stoplamp switch. Use the J 39200 Digital Multimeter (DMM) to measure battery voltage at terminal D of the brake switch connector. Turn ON the ignition, with the engine OFF. Does the voltage measure 10-13 V? If yes, go to step  7. If no, go to next step.
    6. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
  6. Test the brake fuse circuit (CKT 441) for an open. Repair as necessary. After repairs, go to step  16.
  7. Turn ON the ignition, with the engine OFF. Install a fused jumper wire from terminal C to terminal D of the TCC/Stoplamp switch connector. Probe the PCM connector terminal C1-33 with the test lamp. Does the test lamp illuminate? If yes, go to step  9. If no, go to next step.
    8. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
  8. Test the TCC brake switch signal circuit (CKT 420) for an open. Repair as necessary. After repairs, go to step  16.
  9. Replace the TCC/Stoplamp switch. See ADJUSTMENTS in appropriate DISC & DRUM article in BRAKES. After repairs, go to step  16.
  10. Turn ON the ignition, with the engine OFF. Apply and hold the brake pedal. Install a new fuse while keeping the brake pedal applied. Does the fuse open with the brake pedal applied? If yes, go to next step. If no, go to step  12.
    11. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
  11. Test the brake fuse circuit (CKT 441) for a short to ground. Repair as necessary. After repairs, go to step  16.
  12. With the key in the RUN position, release the brake pedal. Does the fuse open when the brake pedal is released? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  13. Disconnect the PCM connector C1 from the PCM. Additional DTCs may set. Turn ON the ignition, with the engine OFF. Install a new fuse. Do not apply the brake pedal. Does the fuse open? If yes, go to next step. If no, go to step  15.
    14. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
  14. Test the TCC brake switch signal circuit (CKT 420) for a short to ground. Repair as necessary. After repairs, go to step  16.
  15. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  16. Perform the following procedure in order to verify the repair:
    • Select DTC.
    • Select Clear Info.
    • Operate the vehicle under the following conditions:
      1. Turn ON the ignition, with the engine OFF.
      2. The brake pedal is not applied.
      3. Select TCC Brake Switch on the scan tool.

    Does the TCC Brake Switch indicate CLOSED when the brake pedal is not applied, then indicate OPEN when the brake pedal is applied? If yes, system is okay. If no, go to step  1.

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