FMI 14 - Derate Due to Incorrect Engine Run Time
Engine derate due to discrepancy in engine run time.
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 control module (ECM) thinks the engine has been running longer than it actually has, which can cause it to restrict power to prevent damage.
What the computer is actually seeing
The ECM monitors total engine run time through various sensors. If the actual run time differs significantly (usually greater than a few minutes) from the reported run time, it triggers this code.
What a healthy reading looks like
Expected engine run time values should remain within 1.0% of actual run time under normal conditions, typically less than 1 hour of engine runtime in a typical trip report.
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. Inspect engine wiring harness and connectors for damage or corrosion. Fix any issues found. Decision: If no issues, proceed to step 2.
- 22. Check for any ECM updates that may address known issues with engine run time calculations. Decision: If an update exists, apply it. If not, move to step 3.
- 33. Verify proper operation of the engine RPM sensor and any associated sensors providing input to the ECM. Expected voltage should be around 0.5V (idle) and fluctuate up to 5V at full RPM. Decision: If sensor output is normal, go to step 4.
- 44. Clear the fault codes and monitor the engine for reoccurrence. Decision: If code returns, consider ECM replacement.
Common causes
- Faulty engine control module (ECM) software or calibration issue
- Wiring harness damaged or shorted
- Internal sensor failures or discrepancies in sensor communications
- Improperly calibrated engine hours from a recent service or replacement part
Typical repair cost
$$$
Related codes
Frequently asked questions
Can I still drive the truck if this code is triggered?
You can drive it, but there will be reduced power. It's best to address it soon.
Will this code come back after repairs?
If the underlying issue is fixed, it shouldn't come back; if wiring or ECM issues persist, it may.
Why does this code sometimes pair with SPN 691?
Both codes relate to engine run time discrepancies, with SPN 691 typically indicating a more severe fault.
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