This bulletin applies to 2018 GMC Acadia vehicles.
Condition 1: Some customers may comment that the electric parking brake is inoperative. DTCs that may include C028F (left parking brake actuator circuit...C028F 04 06 short to ground) and/or C1586 right park brake actuator circuit C1586 04 06 short to ground).
The cause may be due to water leaking into the rear actuator, creating a short to ground.
If DTCs C028F 04 and/or C1586 04 are set, verify which EPB actuator set the DTC and replaces the actuator.
Condition 2: The electric brake may be inoperative. You may find evidence of a previous actuator repair. The cause may be a software anomaly.
If DTCs are not set and/or the brake actuators have previously been replaced, program the EBCM to the latest available calibration.\
Condition 3: The Service Park Brake lamp may be on. DTCs that may be set in the EBCM include C1587 (left park brake actuator...C1587 0B software sensitivity) and/or C1588 (right park brake actuator...C1588 0B software sensitivity). The cause: software sensitivity caused by a weak battery.
If DTCs are set, program the EBCM to the latest calibration.
