P0504

DTC P0504

Circuit Description

The brake lamp switch is a normally open switch that closes when the brake pedal is depressed. When the brake pedal is depressed, the brake lamp switch supplies signal voltage to the brake lamp switch signal circuit. The brake pedal switch is a normally closed switch that opens when the brake pedal is depressed. The engine control module (ECM) monitors the brake lamp switch signal circuit and the brake pedal switch signal circuit. The ECM monitors the status of the brake lamp switch signal circuit and the brake pedal switch signal circuit to see if they match when the brake pedal is pressed or released.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

* The engine is running.
* If the time from state change of one brake input to when the other brake input changes state (making switch states equal again) is greater than 0.5 second, fail counts increase by 3. When the fail counts reach 39, this DTC sets.

Action Taken When the DTC Sets

When DTC P0504 is set the following will occur:

* The malfunction indicator lamp (MIL) will illuminate.
* The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
* A history DTC is stored

Conditions for Clearing the DTC

* The MIL will turn off after 4 consecutive ignition cycles in which the diagnostic runs without a fault.
* A history DTC will clear after 40 consecutive warm-up cycles without a fault.
* DTC(s) can be cleared by using the scan tool.
* Disconnecting the ECM battery feed for more than 10 seconds

Diagnostic Aids

* Inspect for proper adjustment of the stop lamp switch. Refer to Stop Lamp Switch Adjustment Adjustments.
* Check for intermittent and poor connections. Refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.