Test M: The Brake Warning Indicator Is Always On

PINPOINT TEST M: THE BRAKE WARNING INDICATOR IS ALWAYS ON

Normal Operation
The brake warning indicator alerts the driver if any of the following brake system conditions are present: the parking brake is set, the brake fluid level is low, the ABS module detects a base brake system failure, there is a loss of communication between the instrument cluster (IC) and the smart junction box (SJB), or there is a loss of communication between the instrument cluster (IC) and the ABS module.

When the parking brake is applied, circuit 1309 (RD/YE) to the SJB is grounded by the parking brake switch through circuit 1205 (BK). The SJB receives the ground signal and sends the instrument cluster (IC) a message over the communication network to illuminate the brake warning indicator. When the brake fluid level is low, the brake fluid level switch closes, providing a signal to the SJB on circuit 547 (LG/YE) which is then routed back to the SJB on the signal return circuit 512 (TN/LG). When a base brake system concern is detected, the ABS module sends a signal to the instrument cluster (IC) over the communication network to illuminate the brake system warning indicator.

- DTC B2479 (Brake Park Switch Circuit Short to Ground) - sets on-demand if the SJB detects that the parking brake is applied during the self-test or if there is a short to ground on the parking brake input circuit 1309 (RD/YE).
- DTC C1189 (Brake Fluid Level Sensor Input Short Circuit to Ground) - sets on-demand and continuously if the SJB detects that the brake fluid is low or there is a short to ground on the brake fluid level input circuit 547 (LG/YE).

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake switch
- Brake fluid level switch
- SJB
- Instrument cluster (IC)

M1-M4:

M5-M7:

M8-M10: