Test I: The BRAKE Warning Indicator Is Always On

PINPOINT TEST I: THE BRAKE WARNING INDICATOR IS ALWAYS ON

Normal Operation
The parking brake switch and the brake fluid level switch (part of the master cylinder) are hardwired to the instrument cluster (IC). The BRAKE warning indicator uses 3 inputs. The first input is provided by the parking brake switch, and when applied, provides a ground signal to the instrument cluster (IC), illuminating the BRAKE warning indicator. The second input is controlled by the brake fluid level switch. When the brake fluid level is low, the brake fluid level switch closes and provides a ground to the instrument cluster (IC) to illuminate the BRAKE warning indicator. The third input is for the electronic brake distribution (EBD) and is transmitted from the ABS module over the communication network when a base brake system concern is detected.

When the parking brake is applied, circuit 409 (TN/BK) is grounded through the parking brake switch and circuit 57 (BK). The parking brake applied ground is supplied to the instrument cluster (IC) through the brake fluid level switch and circuit 977 (VT/WH). The instrument cluster (IC) receives the ground signal and illuminates the BRAKE warning indicator.

When the brake fluid level is low, circuit 977 (VT/WH) to the instrument cluster (IC) is grounded through the brake fluid level switch and circuit 57 (BK). The instrument cluster (IC) receives the ground signal and illuminates the BRAKE warning indicator.

When a base brake system concern occurs, the ABS module sends a signal to the instrument cluster (IC) over the communication network to illuminate the BRAKE warning indicator. If communication between the instrument cluster (IC) and the ABS module is lost, the instrument cluster (IC) turns on the BRAKE warning indicator.

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

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I8: