Brake Lamp Circuits and Conditions

The red BRAKE warning lamp in the Instrument Panel Cluster (IPC) is powered through the IP fuse (fuse #1 in the front fuse panel) through circuit 250, and receives 12 volts any time that the ignition is in the "run" position. There are two methods by which the BRAKE lamp can be turned on, including:

1. Grounding circuit 852

2. The Body Computer Module (BCM) can turn the BRAKE lamp on by means of the serial data communication link (circuit 800)

BCM ENABLE BY SERIAL DATA COMMUNICATION

The BCM turns the BRAKE lamp on via the serial data link during the IPC segment check at key on. The BCM will also turn the lamp on whenever it receives a low fluid input on pin 3D1. The fluid level sensor grounds circuit 853 when a low fluid level is detected.

CIRCUIT 852

If circuit 852 is grounded for any reason, the BRAKE lamp will be turned on. Several different components can turn the BRAKE lamp on through circuit 852, including:

EBCM (Pin 13)

The EBCM will ground pin 13 if certain failure codes are set. If the EBCM has turned the BRAKE lamp on, it will not hold the lamp on during ABS diagnostic mode (the lamp will be allowed to flash).

Pressure Monitoring Module - Sensor Block (Pin 5)

The pressure monitoring module will ground circuit 852 if low accumulator pressure or an internal pressure switch failure is detected. The BRAKE lamp is turned on when decreasing accumulator pressure reaches approximately 1400 psi (9650 kPa). The BRAKE lamp is turned off when increasing pressure reaches approximately 2100 psi (14,500 kPa).

If conditions exist which would cause the BRAKE lamp to be turned on, the pressure monitoring module will also signal the EBCM by grounding the system fault line (circuit 837); when the EBCM senses that circuit 837 has been grounded, anti-lock function is disabled.

If the pressure monitoring module has turned the BRAKE lamp on, the lamp will not go out or flash during ABS diagnostic mode.

Parking Brake Switch

The parking brake switch will also ground circuit 852 when the parking brake pedal is applied. If the parking brake switch is holding the BRAKE lamp on, the lamp will not go out or flash during ABS diagnostic mode.