Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsGauges, Warning Devices, and Driver Information Systems Diagnosis and RepairMedium
A customer reports that the engine oil pressure warning light illuminates only when making a sharp left turn. The oil level is correct, and there are no engine noises. Which diagnostic step should the technician perform FIRST?
- AInspect the oil pan for dents or damage
- BReplace the oil pressure sensor
- CCheck for loose or frayed wiring to the oil pressure sensor
- DPerform an engine oil pressure test with a mechanical gauge
Show answer & explanationAnswer & explanation
Correct answer: C. Check for loose or frayed wiring to the oil pressure sensor
The symptom of the light illuminating only during a sharp left turn strongly suggests a wiring issue that is being flexed or shorted during the turn. Checking for loose or frayed wiring to the sensor should be the first step, as it's a simple, non-invasive check that aligns perfectly with the described intermittent, directional fault.
Why the other options are wrong
- A. A dented oil pan could cause oil starvation, but it would likely manifest under hard acceleration, braking, or sustained turns, not just a sharp left turn, and usually with engine noise.
- B. Replacing the sensor without further diagnosis is premature, especially given the directional nature of the fault, which points away from sensor failure.
- D. While an oil pressure test is good practice, the directional nature of the fault makes a wiring issue more likely than an actual oil pressure drop, which would typically occur under different conditions.
Directional Electrical Faults
Intermittent electrical problems that occur only when the vehicle is in a specific orientation or performing a specific maneuver, often indicating stressed or damaged wiring.
- Commonly caused by wiring rubbing, flexing, or shorting against the chassis.
- Requires careful visual inspection of harnesses in areas of movement.
- Can be difficult to reproduce consistently in a static shop environment.
Memory trick: Turn and the light ignites? Wires are the likely culprits, not the parts!