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DTC P0504 — MT

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0504 00: Brake Switch Circuits 1-2 Not Plausible

Circuit/System Description

The engine control module (ECM) monitors the brake light switch signal circuit and the cruise control release signal circuit every 100 ms. The ECM monitors the status of the brake light switch signal circuit and the cruise control signal circuit to see if they match when the brake pedal is pressed or released.

Conditions for Running the DTC

    • The ignition is ON.
    • The cruise switch is ON.
    • Ignition voltage is between 9-16 V.

Conditions for Setting the DTC

The status of the brake light switch input to the ECM and the cruise/brake switch input to the ECM do not match for at least 2 s continuously, for 10 occurrences. Each time the signals match, then do not match at counter increments. When the counter reaches 10, this DTC will set.

Action Taken When the DTC Sets

When DTC P0504 00 is set, the following will occur:

    • The cruise control system becomes disabled.
    • The ECM will function as if the brake pedal is not pressed.
    • DTC P0504 00 is a type C DTCs.
    • The malfunction indicator lamp (MIL) will not illuminate.

Conditions for Clearing the DTC

    • The status of the brake light switch input to the ECM and the cruise/brake switch input to the ECM match for at least 2 s continuously for both the pressed position and the released position.
    • A current DTC last test failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles if no failures are reported by this or any other non emission related diagnostic.

Reference Information

Schematic Reference

Exterior Lamps Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Ignition ON, observe the function of the brake lights while applying and releasing the brake pedal. The brake lights should turn ON and OFF as the brake pedal is applied and released.
  2. If the brake lights are always ON or always OFF, refer to Stop Lamps Malfunction .
  3. Observe the scan tool Brake Pedal Switch parameter while applying and releasing the brake pedal. The parameter should change from Active to Inactive.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the B22 Brake Pedal Position Sensor.
  2. Ignition ON, verify that a test lamp illuminates between B+ and the low reference circuit terminal A.
  3. If the test lamp does not illuminate, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
  4. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal C and ground.
  5. If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
    If less than the specified range, test the 5 V reference circuit for an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
  6. Ignition OFF, reconnect harness connector at the B22 Brake Pedal Position Sensor.
  7. Disconnect the appropriate harness connector at the K20 Engine Control Module.
  8. Connect a test lamp between the appropriate harness connector terminal listed below and ground:
  9. • With 2H0, K20 Engine Control Module harness connector terminal 58 X1
    • With LNP, K20 Engine Control Module harness connector terminal 78 X1
  10. Ignition ON, push and release the brake pedal. The test lamp should turn ON and OFF when changed between pushed an released brake pedal.
  11. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
    If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
  12. Verify that DTC P0571 00 is not set.
  13. If DTC P0571 00 is set, replace the K20 Engine Control Module. Clear the DTC and road test the vehicle. If the DTC resets, replace the K9 Body Control Module.
  14. If all circuits test normal, test or replace the B22 Brake Pedal Position Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Brake Pedal Position Sensor Replacement : Left Hand Drive
    •  Brake Pedal Position Sensor Calibration
    • Control Module References for control module replacement, setup, and programming
   


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