Home Tips & Tricks 2001 Chevrolet C-Series Medium Duty Truck B7 Auxiliary Brake Warning Indicator Always...

2001 Chevrolet C-Series Medium Duty Truck B7 Auxiliary Brake Warning Indicator Always On

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Download Circuit Description The auxiliary brake system provides hydraulic fluid flow within the brake booster if the engine is OFF and the brake is applied. The system consists of the following 3 basic components: • The power brake booster pump motor relay • The power brake booster fluid flow switch • The power brake booster pump motor The multifunction alarm module (MFAM) performs a 4 second bulb check on the AUX BRAKE indicator immediately after the engine is cranked or started. The MFAM illuminates the indicator by supplying voltage to the lamp. During the bulb check, the MFAM also performs a diagnostic which tests the power brake booster pump motor relay, the power brake booster fluid flow switch and the power brake booster pump circuitry for electrical faults. The AUX BRAKE indicator remains illuminated if the MFAM detects an electrical fault in the system. The MFAM also sounds an audible warning when the AUX BRAKE indicator illuminates. Test Description The numbers below refer to the step numbers on the diagnostic table. 3. This step tests if the multifunction alarm module is supplying voltage to the brake warning indicator supply voltage 2 circuit.