Automobile & Light Truck Certification Test A5 BrakesAnti-lock Brake System (ABS) Diagnosis and RepairMedium
A technician is performing a diagnostic procedure on an ABS system with a persistent C0110 fault code (Pump Motor Circuit Malfunction). After verifying power and ground to the ABS hydraulic control unit (HCU) and checking the continuity of the pump motor's internal windings, the technician suspects an issue with the pump motor relay. Where is the ABS pump motor relay MOST commonly integrated or located in modern ABS systems?
- AWithin the ABS control module, integrated into the HCU assembly
- BBehind the dashboard, accessible via the glove compartment
- CMounted on the firewall, separate from the HCU
- DAs a standalone relay in the under-hood fuse box
Show answer & explanationAnswer & explanation
Correct answer: A. Within the ABS control module, integrated into the HCU assembly
In many modern ABS systems, the pump motor relay is integrated directly into the ABS control module, which is often bolted to the hydraulic control unit (HCU). This design simplifies wiring and packaging, but means the relay isn't a separately replaceable component.
Why the other options are wrong
- B. Relays are generally not located inside the passenger compartment for high-current applications like the ABS pump motor.
- C. Mounting on the firewall separate from the HCU is less common than integration, especially for a critical component like the pump motor relay.
- D. While some older or simpler systems might use an external relay, it's less common for the primary ABS pump motor in modern integrated units.
ABS Pump Motor Relay Integration
In many contemporary ABS systems, the high-current relay that powers the ABS pump motor is integrated directly into the ABS control module, which is typically part of the hydraulic control unit (HCU) assembly.
- Often not a separately replaceable component.
- Simplifies wiring and packaging.
- Requires replacement of the entire module/HCU if the relay fails.
Memory trick: Pump Power: Module's Built-in Brain!