ASE G1 Auto Maintenance and Light RepairBrakesEasy
A technician is diagnosing an Antilock Brake System (ABS) warning light on the dashboard. After scanning the vehicle's computer, a Diagnostic Trouble Code (DTC) C0200, indicating a 'Left Front Wheel Speed Sensor Circuit Malfunction,' is retrieved. Which of the following is the MOST appropriate initial diagnostic step?
- AReplace the ABS control module.
- BBleed the brake hydraulic system.
- CInspect the left front wheel speed sensor and its wiring for damage.
- DPerform a road test to confirm the ABS light operation.
Show answer & explanationAnswer & explanation
Correct answer: C. Inspect the left front wheel speed sensor and its wiring for damage.
A specific DTC for a wheel speed sensor circuit malfunction directly points to an issue with that sensor or its wiring. The most logical first step is to visually inspect the implicated component for obvious damage, corrosion, or disconnections before considering more complex or expensive repairs.
Why the other options are wrong
- A. Replacing the ABS control module is a last resort after ruling out simpler issues, especially with a specific sensor code.
- B. Bleeding the hydraulic system is unrelated to a wheel speed sensor circuit malfunction.
- D. A road test might confirm the light is on, but it won't diagnose the root cause of the C0200 code. The code already indicates the problem.
ABS DTC Diagnosis
When an ABS warning light is on and a specific DTC is retrieved, the first diagnostic step is to visually inspect the component and wiring indicated by the code.
- DTCs guide diagnosis
- Visual inspection first
- Check connectors and wiring
Memory trick: Code points the way, inspect it today!