What it means
The control module monitors the voltage signal from engine oil pressure sensor or switch B. It sets this code when the signal falls below the calibrated range; the code alone does not confirm that actual oil pressure is low.
At a glance
- Usually lights the check-engine light
How it works
Engine oil pressure sensor or switch B sends a voltage signal to the control module for oil-pressure monitoring. P055C sets when that signal drops below the calibrated range; the low electrical reading may come from the circuit or sensor and does not alone prove actual oil pressure is low.
Common causes
Most likely first.
- Signal wire shorted to ground
- Oil pressure sensor or switch B failed
- Open or high-resistance wiring or connector
- Actual oil pressure below the expected range
Symptoms
- Check-engine light may come on
- Oil pressure warning light may come on
- Oil pressure gauge or display may read low or erratically
- Engine noise if oil pressure is actually low
How to diagnose it
- Check the oil level and listen for engine noise; shut the engine off if the oil warning is on or the engine sounds abnormal.
- Record freeze-frame data and compare sensor B live data with the oil-pressure warning and other available readings.
- Inspect the B sensor connector and wiring for corrosion, loose pins, chafing, or a signal wire touching ground.
- Test the B signal circuit for shorts to ground, opens, and high resistance against the manufacturer's specification.
- If the circuit passes, test sensor or switch B and verify actual oil pressure using the manufacturer's specified method.
Common fixes
- Correct a low oil level with the specified oil.
- Clean and secure the sensor B connector.
- Repair a signal wire shorted to ground or other damaged wiring.
- Replace sensor or switch B if it fails testing.
- Repair any confirmed mechanical cause of low oil pressure.
Can I keep driving?
If the oil-pressure warning is on, the engine is noisy, or the reading is low, stop the engine and do not drive; actual low pressure can cause severe engine damage. If the engine seems normal, still limit driving until pressure is checked because the code cannot distinguish a wiring fault from a real pressure problem.
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.