FMI 3 - Engine Cooling Fan Control Circuit
Cooling fan control circuit has a fault detected.
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)
Your engine cooling fan isn’t getting the right signal to turn on or off, which could lead to overheating.
What the computer is actually seeing
The engine control unit notices an abnormality in the signal received from the cooling fan control circuit, indicating a malfunction in the fan or its control system.
What a healthy reading looks like
Expected operational voltage range is between 0.5V (off) to 12V (fully on) depending on the fan speed required.
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 fan wiring and connectors for damage or corrosion. Look for any loose connections. If found, repair or replace as necessary. Decision: If wiring is good, proceed to next step.
- 22. Test the cooling fan operation by applying direct battery voltage to the fan. It should spin up immediately. Decision: If the fan operates normally, suspect the control circuit; if not, replace the fan.
- 33. Check the fan relay operation by swapping it with another relay of the same type. If the fan works, replace the relay. Decision: If still not operational, check the control signal from the ECU.
- 44. Inspect the ECU for any fault codes or software issues and confirm your device is up to date with programming. If ECU is faulty, replace the unit.
Common causes
- Faulty cooling fan
- Open or short in the wiring harness
- Bad fan relay
- Faulty engine control unit (ECU)
Typical repair cost
$$
Related codes
Frequently asked questions
Can I still drive the vehicle with this code?
It's drivable, but monitor the temperature closely to avoid overheating.
Will this code come back after I clear it?
If the underlying issue isn't fixed, it will likely return after cycling the ignition or during normal operation.
Why does this code pair with SPN 521?
SPN 521 is related to the cooling fan request signal, often indicating a problem with the fan system.
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