FMI 18 - Active Fault Detected in the Engine Control Module
The engine control module has detected a fault and logged an active fault code.
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 engine's computer found something wrong that it couldn't fix on its own and has triggered a warning. This usually means there's an issue with the engine's performance or sensors.
What the computer is actually seeing
The engine control module (ECM) receives input from various sensors about engine performance. When it detects something outside normal parameters, such as a sensor reading drastically either too high or too low, it sets SPN 2560.
What a healthy reading looks like
Normal sensor readings vary by type, but for example, an engine coolant temperature sensor typically sends a signal between 0.5 to 4.5 volts; anything outside this range might trigger the fault.
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 wiring and connectors related to the affected sensors for damage or corrosion.
- 2Verify sensor operation with a multimeter per manufacturer specifications, checking for expected voltage or resistance values.
- 3Inspect the ECM for any signs of damage or corrosion at the connectors.
- 4If everything tests fine, perform a reset of the ECM and monitor for codes reappearing.
Common causes
- Faulty sensor(s)
- Bad wiring or connections
- Failed ECM
- Improperly calibrated sensors
- Power or ground issues to the ECM or sensors
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended to drive without addressing the underlying issue as it could lead to further engine damage.
Will this code come back after clearing it?
It may return if the underlying issue isn't resolved or if a sensor is faulty.
Why is this code paired with other codes?
Multiple codes can be logged if different components are connected to the same system or affected by the same underlying issue.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →