MID 128 - Engine Oil Pressure Sensor Voltage Too High
The engine oil pressure sensor is sending a high voltage signal to the ECM.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The oil pressure sensor measures how much oil is circulating in the engine. If it reports too much voltage, it means the sensor may be faulty or there’s an issue in the wiring, making the computer think there's a problem with the oil pressure.
What the computer is actually seeing
The engine control module (ECM) is reading a voltage from the oil pressure sensor that exceeds 4.5 volts, which is above its normal operating range.
What a healthy reading looks like
Normal oil pressure sensor output should be between 0.5 to 4.5 volts when the engine is running at warm idle.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 1Check the engine oil level and condition; ensure it's within the recommended range. If it’s too high, drain excess oil and retest.
- 2Inspect the wiring and connectors to the oil pressure sensor for damage, corrosion, or loose connections.
- 3Using a multimeter, measure the voltage at the oil pressure sensor connector while the engine is running. It should be between 0.5 to 4.5 volts. If it's over 4.5 volts, continue to step 4.
- 4Replace the oil pressure sensor if steps 1 through 3 show no issues and the voltage is still too high.
- 5If the problem persists after sensor replacement, check for ECM issues or faults in the oil delivery system.
Common causes
- Faulty oil pressure sensor
- Damaged wiring or connectors in the oil pressure sensor circuit
- Oil pressure issues (too high due to overfilling or malfunctioning pump)
- ECM malfunction
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
While you may be able to drive, you risk damaging your engine due to potential oil pressure issues; it's better to address this soon.
Can this code reset itself?
Yes, it can reset if the problem is intermittent or resolved, but a persistent issue needs to be fixed first.
Why does this code come with other SPN codes?
It often pairs with related codes for oil pressure or sensor issues, indicating multiple potential problems in the system.
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