ASE A4 Suspension and SteeringSteering System Diagnosis and RepairMedium
A vehicle with an electronic power steering (EPS) system develops an intermittent loss of power assist. A scan tool shows no active DTCs, but several 'history' codes related to low system voltage (U0100 - Lost Communication with ECM/PCM) and random misfires. All battery and charging system tests pass. What is the MOST likely cause of the intermittent assist loss?
- AExcessive current draw from an unrelated component.
- BA faulty EPS motor.
- CA failing EPS control module.
- DIntermittent electrical connection or ground issue to the EPS system.
Show answer & explanationAnswer & explanation
Correct answer: D. Intermittent electrical connection or ground issue to the EPS system.
Intermittent issues with no active DTCs, but history codes related to communication and voltage, strongly suggest an intermittent electrical connection, such as a loose or corroded ground, or a damaged power wire to the EPS system. The random misfires might be a symptom of the same underlying electrical instability affecting other modules.
Why the other options are wrong
- A. Excessive current draw from an unrelated component would likely cause a charging system issue, which was tested and passed.
- B. A faulty motor would likely trigger a specific motor-related DTC and be more consistent.
- C. A failing module would likely set an internal fault DTC and be more consistent, or completely fail.
Intermittent Electrical Faults
Sporadic malfunctions in electronic systems, often caused by loose connections, corroded terminals, or damaged wiring, resulting in intermittent symptoms and often history (non-active) diagnostic codes.
- Symptoms are inconsistent and hard to reproduce.
- Often associated with communication or voltage-related history DTCs.
- Diagnosis involves checking wiring harness, connectors, and grounds.
Memory trick: Intermittent means check the connections.