Normal Operation

WARNING: This page is about a different car, the 2011 Mercury Milan, 2011 Lincoln MKZ, and 2011 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.

When the combustion engine is not running, the electric vacuum pump is utilized to maintain a vacuum inside the brake booster. The ABS module controls the electric vacuum pump through the use of a mechanical relay located in the Battery Junction Box (BJB) and a solid state relay located in the auxiliary relay box. The mechanical relay provides power to the solid state relay. The solid state relay provides power to the electric vacuum pump motor. When the ignition is in the RUN position, the ABS module closes the mechanical relay. After the vehicle is started (the ready indicator is illuminated), the ABS module activates the solid state relay as necessary to maintain a vacuum inside the brake booster.

Fused battery voltage is provided to the mechanical relay from the BJB. When the ignition switch is turned to the RUN position, the ABS module grounds the output side of the mechanical relay solenoid. This closes the mechanical relay and send voltage to the solid state relay. When it is necessary to build vacuum in the brake booster, the ABS module grounds the solid state relay along circuit. The solid state relay then sends voltage to the vacuum pump and BJB fuse 37. The voltage passes through BJB fuse 37 (5A) and is delivered to the ABS module along circuit. The ABS module uses this voltage input to monitor the vacuum pump.

The logic internal to the solid state relay provides circuit protection for the vacuum pump circuit. If a short to ground on circuit is detected, the relay stops applying power until the short has been repaired.

If a vacuum pump DTC is set, the red brake warning indicator illuminates and the combustion engine runs to supply vacuum to the brake booster.

DTC C101C:01 (Brake Vacuum Pump: General Electrical Failure) - If the ABS module detects a short to ground, an open or high resistance on circuits CBB37 (WH), CCB29 (WH/VT) and CCB30 (GY/VT), or an open or high resistance, this DTC sets.
DTC C101C:71 (Brake Vacuum Pump: Actuator Stuck) - If the ABS module detects that vacuum in the brake booster is increasing when the vacuum pump is commanded off and the combustion engine is not running, this DTC sets.

This pinpoint test is intended to diagnose the following:

Fuses
Wiring, terminals or connectors
Electric vacuum pump solid state relay
Electric vacuum pump solid mechanical relay
Electric vacuum pump
ABS module