The oil pressure sensor (or oil pressure switch) reports engine oil pressure to the gauge, the warning light and often the engine computer. A failing sensor can make the gauge read zero, maximum or jump around, or make the oil light flicker, while the engine actually has normal pressure. Because real low oil pressure destroys an engine quickly, the first step is always to confirm pressure with a mechanical gauge.
Sensor vs switch
- Oil pressure switch: a simple on/off switch that turns the warning light on below a set pressure.
- Oil pressure sensor: sends a variable signal so a gauge can show actual pressure; the computer may use it for warnings or for systems such as cylinder deactivation.
Bad oil pressure sensor symptoms
- Gauge reading zero, pegged high, or swinging while the engine sounds normal
- Oil pressure light flickering at idle or coming on at random
- Oil leaking from the sensor body or connector
- Check engine light with codes P0520, P0521, P0522 or P0523
Sensor fault or real low oil pressure?
| Clue | Points to |
|---|---|
| Mechanical gauge reads normal while the dash reads low | Sensor or wiring |
| Mechanical gauge also reads low | Real low pressure: oil level, viscosity, pickup, pump or bearings |
| Ticking or knocking noise | Real low pressure; stop the engine; see engine knocking |
| Gauge jumps instantly between zero and full | Electrical fault in the sensor or connector |
A common rule of thumb is roughly 10 psi of oil pressure per 1,000 RPM when warm, but the specification for your engine is what matters. See low oil pressure for causes and what pressure is normal.
Where is the oil pressure sensor?
Location varies: near the oil filter, on the side of the block, near the front cover, or at the back of the engine under the intake manifold on some V8s. On some GM V8s the sensor and a small filter screen beneath it are a known failure point, causing false low readings. Follow the wire from the gauge circuit or check your service information.
How to test and replace it
- Install a mechanical gauge in the sensor port and compare readings cold and hot, at idle and around 2,000 RPM.
- If pressure is normal, check the connector, reference voltage, ground and signal.
- Replace the sensor with the engine cool; use a sensor socket and thread sealant only if the part calls for it.
- Start the engine and check for leaks and a steady reading.
If oil pressure really is low
Check oil level and viscosity first, then the pickup screen, the pump and bearing clearances. On engines with lifter or cam damage from low pressure, see lifter tick and spun rod bearings. If the bottom end is worn, a replacement may cost less than a rebuild; compare engines by code on our engines page.
More guides: oil pressure light on · bad oil pump symptoms.
Trouble codes: P0524 Engine Oil Pressure Too Low · all OBD2 codes.
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