P1574 - FAULT CODE - OBD2

P1574 BUICK, CADILLAC, CHEVROLET, FORD, GMC: STOP LAMP SWITCH CIRCUIT

The stop lamp switch circuit diagnostic test is performed when a sudden decrease in speed of a non-powered wheel is detected, and such a stop must be caused by the application of the brakes.

The speed of the non-drive wheel and the status of the stop lamp switch are provided to the Powertrain Control Module (PCM) via serial data from the EBCM (Electronic Brake Control Module).

If a 4.02 km/h or greater decrease in non-drive wheel speed occurs within 0.4 seconds and a TCC transition occurs without a brake light switch change, diagnostic code P1574 OBDII will be set.

• Check Engine Lamp illuminated.

The reasons for setting the P1574 OBD2 fault code are:

• The stop lamp switch may have bad wiring.
• The stop lamp switch circuit could have a short.
• The stop lamp switch could be in bad condition.

To troubleshoot DTC P1574 OBDII code you must do the following:

• Consult the TSBs.
• Using an automotive scan tool you must retrieve the DTCs stored in the PCM memory, paying more attention to the EBCM or C codes. Diagnose those codes.
• Inspect the condition of the stop lamp switch circuit wiring harness. Checks for deficiencies due to burns or wear and performs repairs as required based on the condition of the wiring.
• Verify that the stop lamp switch signal circuit is not shorted open. If you discover such situations, make the appropriate corrections.
• If after performing the above checks you still get the P1574 code, suspect a switch in poor condition that requires replacement.