What is SPN 111 FMI 17 & How to Solve It?

What is SPN 111 FMI 17:

SPN 111 refers to Engine Coolant Temperature, and FMI 17 indicates a data mismatch or intermittent signal — often caused by a failing or loose sensor.

This may result in poor fan control or improper warm-up fueling.

‍

Why This Happens

• Coolant temp sensor loose or corroded.
• Wiring harness intermittent.
• ECM receiving unstable signal.
• Engine vibration causing sensor dropout.

‍

How to Fix It

1. Inspect and clean the coolant temp sensor connector.
2. Test the sensor resistance when cold and hot.
3. Replace the sensor if signal drops on live diagnostics.
4. Reseat or replace damaged wiring.
5. Clear the code and verify stable signal.

‍

How to Avoid It Before It Happens

1. Replace temperature sensors with each coolant flush.
2. Secure wiring near sensor to prevent vibration damage.
3. Monitor warm-up time and idle behavior.