Test A: The Red Brake Warning Indicator Is Always on

Test A: The Red Brake Warning Indicator is Always On

Refer to Vehicle/Diagrams, Instrument Cluster for schematic and connector information.

Normal Operation
The red brake warning indicator is located in the instrument cluster and illuminates during prove out, when the brake fluid in the brake master cylinder reservoir is below a specific level, when the parking brake is engaged or when the brake fluid level switch is disconnected. The instrument cluster receives a ground input on circuit 162 (LG/RD) when the parking brake has been applied through circuit 57 (BK), turning on the brake warning indicator. The instrument cluster provides a voltage reference signal to the brake master cylinder fluid level switch through circuit 531 (DG/YE) and through the switch and back to the instrument cluster on circuit 512 (TN/LG). The circuit then grounds in the cluster through an 820 ohm resistor, dropping the voltage reference signal (the instrument cluster is monitoring) approximately in half. When the brake fluid level is low, the brake fluid level switch closes to ground through circuit 57 (BK). The voltage reference signal the instrument cluster is sending to the brake fluid level switch drops to zero, which signals the cluster to turn on the brake warning indicator. If circuit 531 (DG/YE), circuit 512 (TN/LG) or the brake fluid level switch opens, the voltage reference signal the instrument cluster is sending out on circuit 531 (DG/YE) goes to the full voltage reference (12 volts), which also signals the instrument cluster to turn on the brake warning indicator.

Possible Causes
^ Low brake fluid level
^ Parking brake engaged
^ Circuit open
^ Circuit shorted
^ Parking brake switch
^ Low brake fluid level switch
^ Instrument cluster

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