What is SPN 100 FMI 31 & How to Solve It?

What is SPN 100 FMI 31:

This fault indicates the ECM detected abnormal behavior from the engine oil pressure circuit without a defined cause.

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Why This Happens

• Oil pressure sensor failing or reading inconsistently.
• Dirty or degraded engine oil.
• Wiring signal noise or poor grounding.
• Engine oil pump performing below spec.

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How to Fix It

1. Check oil level and oil condition.
2. Test oil pressure manually using a gauge.
3. Inspect and repair sensor wiring and connections.
4. Replace the oil pressure sensor if values are unstable.
5. Clear the fault and verify consistent pressure under load.

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How to Avoid It Before It Happens

1. Follow the recommended oil and filter change schedule.
2. Replace oil pressure sensors at intervals suggested by the OEM.
3. Log pressure fluctuations and address them early.