P1574

Circuit Description
The Brake Lamp Switch is a normally open switch. When the Brake Lamp Switch is closed, the TAC module senses ignition voltage on the Brake Lamp Switch signal circuit.
If the TAC module senses a voltage on the Brake Lamp Switch signal circuit when the Brake Lamp Switch should be open, this DTC sets.

Conditions for Running the DTC
^ The engine speed is greater than 700 RPM.
^ The wheel speed must be greater than 30 MPH in order to enable the diagnostic. The diagnostic will disable when the wheel speed is below 10 MPH.
^ The vehicle speed is decreasing at a rate greater than 10.4 MPH over a one second period.

Conditions for Setting the DTC
^ The TAC does not detect voltage on the Brake Lamp Switch circuit when the Brake Lamp Switch should be closed.
^ The above conditions present for 1.5 seconds.

Action Taken When the DTC Sets
^ The PCM stores the DTC information into memory when the diagnostic runs and fails.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

Conditions for Clearing the MIL/DTC
^ A last test failed (current DTC) clears when the diagnostic runs and does not fail.
^ A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
^ Use a scan tool in order to clear the MIL/DTC.

Diagnostic Aids

Important:
^ Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
^ For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter kit J 35616-A. Using this kit prevents damage to the harness/component terminals.
1. Test drive the vehicle if you cannot find a problem with the switch or the circuit. An intermittent condition may be duplicated on a test drive.
3. For an intermittent condition, refer to Symptoms. Symptom Related Diagnostic Procedures

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if the fault is present.
5. This step verifies that the B+ feed is present at the Stop Lamp switch.
11. Test for a short to ground between the fuse and the Stop Lamp switch and between the Stop Lamp switch and the TAC module.