Automobile & Light Truck Certification Test A5 BrakesAnti-lock Brake System (ABS) Diagnosis and RepairMedium
A technician is diagnosing an ABS warning light on a vehicle that uses an integral ABS design (ABS control module and hydraulic control unit are one assembly). The scan tool indicates a C0110 fault code, 'Pump Motor Circuit Malfunction'. Which of the following is the MOST appropriate initial diagnostic step?
- AReplace the entire integral ABS module assembly.
- BCheck the power and ground connections to the integral ABS module.
- CBleed the brake system using a pressure bleeder.
- DPerform a continuity test on the pump motor windings.
Show answer & explanationAnswer & explanation
Correct answer: B. Check the power and ground connections to the integral ABS module.
A 'Pump Motor Circuit Malfunction' indicates an issue with the electrical circuit powering the ABS pump. Before condemning the entire expensive integral ABS module, it's crucial to verify that the module itself is receiving proper power and ground. Without correct power and ground, the pump motor cannot operate, regardless of its internal condition. This is a fundamental electrical diagnostic step.
Why the other options are wrong
- A. Replacing the entire module without proper diagnosis is costly and may not fix the root cause if it's an external wiring issue.
- C. Bleeding the brake system is a hydraulic procedure and will not resolve an electrical circuit malfunction for the pump motor.
- D. While important, testing the pump motor windings directly is difficult without disassembling the integral module and should only be done after verifying external power/ground.
ABS Pump Motor Circuit Diagnosis
Troubleshooting an electrical fault with the ABS hydraulic pump motor.
- A C0110 code indicates a circuit malfunction.
- Always start by verifying power and ground to the ABS module.
- The pump motor is critical for recirculating fluid and building pressure during ABS events.
Memory trick: Pump motor circuit fault? Check the module's power first, before you start to shout!