GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Holden 🢒 2008 🢒 Epica 🢒 DTC 🢒 DTC P0504

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 Descriptors

DTC P0504: Brake Switch Circuit 1 - 2 Correlation

Circuit/System Description

The stop lamp switch signal circuit is a direct hard-wire input from the fuse block to the engine control module (ECM). The module monitors the stop lamp switch signal circuit to detect when the brake pedal has been applied. The ECM monitors the stop lamp switch circuits to determine when the brake pedal is applied.

Conditions for Running the DTC
    • The engine is running.
    • Battery voltage is greater than 11.5 volts.

Conditions for Setting the DTC

The ECM detects a non-matching low or high voltage signal on the stop lamp switch signal circuit when the brakes are applied.

Actions Taken When the DTC Sets
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The cruise control system is disabled.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists.
    • A history DTC will clear after 100 malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

    •  Exterior Lights Schematics
    •  Cruise Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cruise Control Description and Operation

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Verify that the stop lamps work properly. Refer to Exterior Lighting Systems Description and Operation.

⇒If the stop lamps do not work properly, refer to Stop Lamps Always On or Stop Lamps Inoperative.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the ECM.
  2. Connect a test lamp between the signal circuit terminal K54 (2.0L) or K53 and ground.
  3. Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
    4. ⇒If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the stop lamp switch.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal and the fuse is good, replace the stop lamp switch.
  4. Ignition OFF, connect a test lamp between the signal circuit K17 (2.0L) or K83 and ground.
  5. Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
    6. ⇒If the test lamp is always ON, refer to Stop Lamps Always On.
    ⇒If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit test normal and the fuse is good, replace the stop lamp switch.
  6. If all circuits test normal, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Stop Lamp Switch Replacement

Control Module References for ECM replacement, setup, and programming