When there is an unexpected stop, one or more wheels may lock up. In this case, the ABS system takes action based on the information sent by the wheel speed sensors. These sensors indicate the wheels are slowing down quickly, so the ABS system closes the brake fluid flow to the wheel through the inlet valve or coil. In this way, the pressure is released through the output coil.
The ABS pump is in charge of reloading the brake fluid. The ABS pump switch notifies the ABS Control Module when the pump is operating and when to turn the pump on according to the assembler’s application. The ABS pump switch is usually included only on cars that have 4-wheel anti-lock brakes. Frequently, the system performs self-tests to ensure the switch circuit works properly each time the ignition switch is activated.
When the C1100 OBDII fault code is set, it is because the control module detects the ABS pump switch wiring is damaged, causing the circuit to malfunction. Specifically, this code shows the BMC cannot check the ABS pump switch for proper operation once the ignition switch has been activated.