Oil Pressure Low
Indicates low oil pressure in the engine.
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What it means (plain English)
When the engine is running, it should have oil pressure to keep all moving parts lubricated. If the oil pressure drops below a specific level—usually around 5 PSI—this code will trigger, warning you that the engine might not be getting enough oil.
What the computer is actually seeing
The engine control module (ECM) is reading the oil pressure sensor data, which should report a pressure reading; if it drops below 5 PSI, the ECM triggers SPN 959.
What a healthy reading looks like
Normal oil pressure at idle should be between 15-25 PSI and can go up to 40-60 PSI during acceleration, depending on the engine.
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.
- 11. Check the engine oil level; it should be at the recommended level. If low, add oil and check for leaks.
- 22. Inspect the oil pressure sensor wiring and connector for damage or corrosion.
- 33. Test the oil pressure using a mechanical gauge; it should match expected values.
- 44. If the gauge reads low while the sensor is good, assess the oil pump and oil filter.
- 55. Clear the code and see if it returns after driving.
- 66. If the code persists or oil pressure is low, consider further internal engine diagnostics.
Common causes
- Low oil level
- Faulty oil pressure sensor
- Worn engine bearings
- Oil pump failure
- Clogged oil filter
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
If the oil pressure is low, it can lead to engine damage. It’s best to diagnose and fix the problem immediately.
Will this code come back after clearing it?
Yes, if the underlying issue isn’t resolved, the code will likely return.
Why does this code appear with SPN 958?
SPN 958 indicates an oil pressure sensor issue, which can be linked to low oil pressure, causing both codes to appear.
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