P0504

DTC P0504

Circuit Description

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

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0504 Brake Switch Circuit 1-2 Correlation.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The status of the stop lamp switch input to the ECM, and the TCC brake switch/cruise control input to the ECM do not match for at least 2 seconds continuously, for 10 occurrences. Each time the signals match then do not match a counter increments. When the counter reaches 10 the DTC will set.

Action Taken When the DTC Sets

When DTC P0504 is set the following will occur:
- The cruise control is disabled.
- The ECM will function as if the brake pedal is not pressed.
- The control module stores the DTC information into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL) will not illuminate.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

Conditions for Clearing the DTC

- The DTC will clear when the status of the stop lamp switch input to the ECM, and the TCC brake switch/cruise control input to the ECM match for at least 2 seconds 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.
- Clear the DTC with a scan tool.

Diagnostic Aids

- Aftermarket trailer brake controllers must be disconnected before diagnosing DTC P0504 due to they could result in incorrect diagnostics.
- Check for intermittents and poor connections.