What it means
The ECM detects a range/performance fault on the engine oil pressure sensor/switch c. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Engine oil pressure sensor/switch C provides the ECM with an electrical indication of oil pressure. P2D91 sets when that signal is within an electrically plausible range but does not behave as expected, which can result from sensor drift, aging, or displacement at its mounting.
Common causes
Most likely first.
- Sensor characteristic drifted
- Sensor mounting displaced
- Sensor element aged beyond calibration window
Symptoms
- Oil-pressure warning light may be on
- Check-engine light may be on
- Oil-pressure gauge may read inaccurately or fluctuate
- Engine may run noisily if oil pressure is actually low
How to diagnose it
- Review freeze-frame data and sensor C live readings for implausible changes or disagreement with engine conditions when the code set.
- Check the oil level and listen for abnormal engine noise before treating the fault as only a sensor issue.
- Inspect sensor C for secure, correct mounting and check its connector and wiring for corrosion, damage, or looseness.
- Compare the sensor C reading with actual oil pressure measured using the manufacturer's procedure to distinguish sensor error from low pressure.
- If actual pressure is normal, test sensor C output and its circuit against the manufacturer's specifications, paying attention to drift or unstable readings.
Common fixes
- Secure sensor C correctly if it is displaced or loose.
- Clean or repair a poor sensor C connector or damaged circuit wiring.
- Replace sensor/switch C if its output has drifted outside the manufacturer's calibration limits.
- Repair a confirmed mechanical oil-pressure problem if measured pressure is abnormal.
Can I keep driving?
If the oil-pressure warning remains on or the engine is noisy, stop and check the oil level; a range/performance fault can mask genuinely low pressure. If the engine sounds normal and there is no warning, limit driving until actual pressure and sensor accuracy are checked.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.