Automobile & Light Truck Certification Test A5 BrakesAnti-lock Brake System (ABS) Diagnosis and RepairMedium
A customer complains that their vehicle's ABS warning light comes on intermittently, usually after driving through heavy rain or puddles. The scan tool reports various intermittent wheel speed sensor fault codes (e.g., C0031, C0034). Upon inspection, the technician finds no visible damage to the sensors or wiring, but notices signs of corrosion in one of the ABS control module's electrical connectors. What is the MOST likely root cause of these intermittent faults?
- AA low-voltage condition from the vehicle's battery.
- BInternal failure of the hydraulic control unit (HCU).
- CContamination and poor connection at the ABS control module connector.
- DA failing ABS pump motor.
Show answer & explanationAnswer & explanation
Correct answer: C. Contamination and poor connection at the ABS control module connector.
Corrosion in an electrical connector, especially one exposed to moisture, creates high resistance and intermittent connections. This can disrupt sensor signals reaching the control module, leading to various intermittent fault codes, particularly when moisture is present.
Why the other options are wrong
- A. A low-voltage condition would likely trigger multiple system-wide codes or general power supply codes, not specifically intermittent wheel speed sensor codes related to moisture.
- B. Internal HCU failure usually involves hydraulic issues or specific solenoid/valve faults, not generic intermittent wheel speed sensor codes.
- D. A failing ABS pump motor would typically generate a specific pump motor fault code and affect braking performance, not multiple intermittent wheel speed sensor codes.
Connector Corrosion Impact
Corrosion in electrical connectors, especially those exposed to environmental factors, can lead to intermittent circuit issues, high resistance, and signal loss. This often manifests as intermittent fault codes in electronic systems like ABS.
- Increases resistance in the circuit.
- Causes intermittent signal disruptions.
- Worsens with moisture exposure.
Memory trick: Rainy Day Faults: Check the Module's Plug!