What This FMI Means
FMI 10 indicates the rate of change of the measured parameter exceeds what the module considers physically plausible. The value may be within the normal operating range, but it changed too rapidly for the real physical system to support. This is a kinematic plausibility fault: the module compares how fast the signal is changing against how fast the underlying physical parameter could realistically change.
For example, a coolant temperature sensor that jumps from 160°F to 240°F in one ECM scan cycle is electrically intact and the values are technically within measured range, but the rate of change is physically impossible — coolant does not heat that quickly. FMI 10 captures this type of signal anomaly that FMI 0 or FMI 2 might miss.
How It Appears With SPN Codes
FMI 10 appears on parameter SPNs where the physical system has inherent rate-of-change limits — temperature sensors, fluid pressure sensors, and position sensors. It is less common than FMI 0, 1, 2, 3, or 4, and when it does appear, it often points to a sensor or connector that produces spike-type interference rather than a steady, drifting fault.
On fuel rail pressure SPNs, an abnormal rate of change can indicate brief pressure drops from injector seal leakage or a failing high-pressure fuel pump. On boost pressure SPNs, FMI 10 may indicate turbocharger surge or a compressor bypass issue. OEM service information specifies the rate-of-change threshold defined for each SPN and the expected diagnostic path.
How to Approach Diagnosis
FMI 10 is best investigated with a data logger or diagnostic software capable of high-speed data capture. A single-value snapshot misses the transient behavior that causes FMI 10. Recording the SPN's value over time while recreating the conditions that trigger the code is the most effective approach — looking for brief spike excursions before the value returns to normal.
Sensor connector integrity is a common cause of spike behavior. Brief signal excursions from 0.5V to 4.9V (or the opposite) caused by an intermittent pin contact look like a rapid physical parameter change to the ECM and trigger FMI 10. Inspect connectors for moisture intrusion, pin fretting, and partially seated terminals.
What Drivers Should Record
Record the exact operating conditions when FMI 10 occurred — vehicle speed, load level, throttle position, gear, ambient temperature, and any recent operational changes. FMI 10 codes that appear only during transitions (hard acceleration, heavy braking, gear shifts) are particularly informative.
Note any associated symptoms such as a brief instrument gauge spike, a momentary power loss, or an intermittent warning lamp alongside the FMI 10 event. These confirm whether the rate-of-change was a real physical event or an artifact of a sensor or wiring issue.
Related Pages
Related Fault Code Pages
- Bendix EC-60 UDS 10 / SPN 793 FMI 10
- Bendix EC-60 UDS 74 / SPN 789 FMI 10
- Bendix EC-60 UDS 106 / SPN 792 FMI 10
- Bendix EC-60 UDS 138 / SPN 790 FMI 10
- Bendix EC-60 UDS 170 / SPN 791 FMI 10
- Bendix EC-60 UDS 202 / SPN 794 FMI 10
- WABCO MM-0112 SPN 789 FMI 10
- WABCO MM-0112 SPN 790 FMI 10
- WABCO MM-0112 SPN 791 FMI 10
- WABCO MM-0112 SPN 792 FMI 10
- WABCO MM-0112 SPN 793 FMI 10
- WABCO MM-0112 SPN 794 FMI 10
- WABCO RSSplus SID 3 FMI 10
- WABCO RSSplus SID 4 FMI 10
- WABCO RSSplus SID 5 FMI 10
- WABCO RSSplus SID 6 FMI 10
Sources
- SAE J1939 Standards Collection SAE International · official · accessed 2026-05-05 · confidence medium
Source: SAE International, SAE J1939 Standards Collection. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - NHTSA Manufacturer Communications Search National Highway Traffic Safety Administration · government · accessed 2026-05-05 · confidence high
Source: National Highway Traffic Safety Administration, NHTSA Manufacturer Communications Search. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
What does 'abnormal rate of change' mean in FMI 10, and how is it different from FMI 2 (erratic)?
FMI 10 means the value is changing faster or more erratically than the physical system should allow. The ECM knows, for example, that engine coolant temperature cannot drop from 200°F to 80°F in a fraction of a second under normal conditions. If a sensor produces that kind of jump, the ECM flags it as an implausible rate of change (FMI 10). FMI 2 is more general — the signal is inconsistent, but the specific type of inconsistency isn't necessarily a rate issue.
Can FMI 10 appear from an intermittent connector problem rather than a failed sensor?
Yes. A connector that momentarily loses contact will cause the signal to drop or spike to the circuit's default value, which appears as a sudden large change. When the contact restores, the reading jumps back — producing a high rate-of-change event even though the physical parameter hasn't actually changed. Connector inspection and wiggle-testing under live monitoring are useful diagnostic steps for FMI 10.
Which systems on a heavy truck commonly produce FMI 10 faults?
Temperature sensors (coolant, exhaust, intake air) and pressure sensors are the most common sources of FMI 10 faults because the ECM has physical models for how quickly these parameters can change. Rapid swings in a reading that the ECM considers impossible given the current operating conditions trigger FMI 10. Exhaust temperature sensors are particularly prone to this when their connectors degrade.