A vehicle with an electric power steering (EPS) system develops a 'notchy' or 'jerky' feeling in the steering wheel that is inconsistent and often disappears and reappears. Diagnostic trouble codes (DTCs) point to an intermittent communication error between the EPS control module and the vehicle's Body Control Module (BCM). Which of the following is the MOST appropriate next diagnostic step?
- AFlush and replace the power steering fluid.
- BPerform a steering angle sensor recalibration.
- CInspect the CAN bus wiring and connectors between the EPS module and BCM.
- DReplace the EPS motor, as it is likely failing intermittently.
Show answer & explanationAnswer & explanation
Correct answer: C. Inspect the CAN bus wiring and connectors between the EPS module and BCM.
DTCs indicating intermittent communication errors between modules strongly suggest a problem with the communication network itself, which is typically the CAN (Controller Area Network) bus. Inspecting the wiring, connectors, and terminals for corrosion, damage, or looseness in the CAN bus circuits between the EPS module and BCM is the logical next step to resolve such communication-related faults.
Why the other options are wrong
- A. Flushing power steering fluid is irrelevant for an electric power steering system, as it does not use hydraulic fluid.
- B. A steering angle sensor recalibration might be needed after repairs, but it won't fix an underlying communication fault.
- D. Replacing the EPS motor without addressing the communication fault is unlikely to resolve the issue and could be costly if the motor is not the root cause.
EPS Intermittent Communication
Intermittent communication errors between an EPS control module and other vehicle modules (e.g., BCM) typically indicate a fault in the CAN bus wiring, connectors, or network integrity, requiring inspection of these components.
- DTCs point to network issue.
- Look for wiring damage, corrosion, loose pins.
- CAN bus is critical for module communication.
Memory trick: Communication broken? Check the wires and connectors.