Engine Oil Pressure Sensor/Switch "A" Circuit Low

What it means

The engine oil pressure sensor signal voltage is below the normal range. The engine oil pressure sensor reports engine oil pressure to the ECU and the oil warning light or gauge. A low signal is usually caused by a short to ground, a missing reference voltage or a failed sensor.

Symptoms

• Check engine light on
• Oil pressure light flickering or staying on
• Oil pressure gauge reading zero or maximum

Probable causes

Most likely first

1. 1Open or shorted 5-volt reference wire from the ECU
2. 2Signal wire shorted to ground
3. 3Unplugged, corroded or loose connector
4. 4Failed sensor
5. 5Another sensor on the same 5V reference circuit shorting it down

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the engine oil pressure sensor connector and wiring (screwed into the engine block or oil filter housing). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the engine oil pressure sensor reading on live data. Compare the reading with a mechanical oil pressure gauge fitted in place of the sensor.
4. 4With the key on and the sensor unplugged, check for about 5 volts on the reference wire and a good ground (under 0.1 V drop) on the ground wire. Back-probe the signal wire with the sensor connected and watch the voltage change smoothly.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Repair the damaged wiring or connector
• Replace the engine oil pressure sensor
• Clear the code and test drive to confirm the repair