Brake Warning Indicator

The IPC uses 3 basic messaged inputs to control the brake warning indicator. The first 2 messages are the parking brake position switch and the brake fluid level switch sent from the BCM. The third is the brake warning indicator request message sent from the ABS module through the BCM.

The parking brake position switch and the brake fluid level switch are hardwired to the BCM through a single signal circuit while using a separate ground to control the input.

The BCM provides reference voltage to both the parking brake position switch and the brake fluid level switch. When the parking brake is applied, the parking brake position switch closes to ground, pulling the parking brake signal circuit low. When a low brake fluid level condition exists, the brake fluid level switch closes to ground, pulling the signal circuit low. If the brake fluid level switch is disconnected, the BCM reference voltage sent to the brake fluid level switch remains high and the brake fluid input is interpreted as normal by the BCM.

When the BCM detects the brake fluid level signal low, the BCM sends the brake fluid level low request to the IPC. When the BCM detects the parking brake signal low, the BCM sends the parking brake warning request to the IPC. When the ABS module detects a base brake system concern or other ABS-related concerns that affect the EBD function, the ABS module sends the brake warning request to the BCM. The BCM then sends the brake warning indicator request to the IPC to illuminate the brake warning indicator.

If the brake fluid level drops and closes the brake fluid level switch, the BCM waits approximately 30 seconds before sending the IPC the brake fluid level low message to illuminate the brake warning indicator.