John Deere Engines SPN 2630 FMI 4 Fault Code: Charge Air Cooler Outlet Temperature Signal Out Of Range Low
Also called Charge Air Cooler Outlet Temperature Signal Out of Range Low, Engine Shutdown Commanded by Application
Charge Air Cooler Outlet Temperature Signal Out Of Range Low · ai-assisted, editor-reviewed · Last updated 2026-07-21
TL;DR
SPN 2630 FMI 4 sets when the charge air cooler outlet temperature sensor signal voltage drops below the sensor's low voltage specification, a reading that corresponds to a temperature higher than what is physically possible. The ECU flags this as a Warning, substitutes a default value of 50° C (122° F), and keeps trying to maintain the engine operating envelope.
Medium severity. This is logged as a Warning, not a shutdown code, and the ECU keeps running on a substituted default temperature. It should still be diagnosed promptly because the ECU is no longer seeing real charge air cooler outlet temperature and is making control decisions on a fixed value instead.
What does John Deere Engines error code SPN 2630 FMI 4 mean?
SPN 2630 FMI 4 means the ECU sees a charge air cooler outlet temperature sensor signal voltage that has dropped below the sensor's own low voltage specification. Oddly, a low voltage on this circuit corresponds to a calculated temperature that is higher than what is physically possible, which is how the ECU recognizes the signal is invalid rather than a real reading.
Once this fault is active, the ECU stops trusting the live sensor input and substitutes a fixed default charge air cooler outlet temperature of 50° C (122° F). It uses that default while it keeps trying to maintain the normal engine operating envelope, so the engine keeps running but without accurate feedback from this sensor.
This is an input low or open-type fault. That points toward a broken or disconnected circuit, a short to ground, or a lost sensor supply, rather than a wire shorted to another powered circuit.
What triggers a John Deere Engines SPN 2630 FMI 4 code?
The fault is displayed whenever the ignition is on and the condition is active: the charge air cooler outlet temperature sensor signal voltage is below the sensor's low voltage specification, corresponding to a temperature higher than what is physically possible for that location.
Common causes of SPN 2630 FMI 4
- Bad or corroded terminals or connector at the charge air cooler outlet temperature sensor
- Bad terminals or connector at the ECU
- Open or short in the wiring harness between the sensor and ECU, including melted, pinched, or chafed wiring
- Intermittent short to ground in the harness
- High resistance in the harness or connectors
- Bad charge air cooler outlet temperature sensor
- Bad ECU connector connection
- Bad ECU
- Bad or outdated ECU software
How to troubleshoot John Deere Engines SPN 2630 FMI 4: first checks
- Inspect the charge air cooler outlet temperature sensor connector for corrosion, moisture intrusion, bent or backed-out pins, and loose terminals before disturbing anything else
- Visually trace the harness between the sensor and the ECU looking for melted, pinched, or chafed insulation, especially anywhere it runs near hot or moving components
- With the connector disconnected, check the sensor circuit for continuity and for an unwanted short to ground or chassis, since a low-voltage fault often points to an open or grounded signal wire
- Check the ECU connector for the same corrosion and terminal issues, since a bad ECU-side connection produces the same symptom as a bad sensor-side connection
- Test the sensor itself against its low voltage specification if the wiring and connectors check out, and swap or bench test it if it's suspect
- Confirm ECU software is current, since outdated ECU software is listed as a possible cause
- If wiring, connectors, and the sensor all test good, suspect the ECU itself
How the code clears
No separate clearing step is listed. The fault is active whenever the ignition is on and the underlying voltage condition is present, so once the wiring, connector, sensor, or ECU issue is repaired and the signal returns to a valid range, the active fault should clear on its own during normal operation. No distinct reset procedure is described.
Frequently asked questions
What does SPN 2630 FMI 4 mean on a John Deere engine?
It means the ECU detected a charge air cooler outlet temperature sensor signal voltage below the sensor's low voltage specification, a reading that corresponds to a temperature higher than physically possible. The ECU treats this as an invalid signal and substitutes a default value of 50° C (122° F) while trying to keep the engine within its normal operating envelope.
Is SPN 2630 FMI 4 a serious fault?
It's logged at a Warning alarm level, not an immediate shutdown. The engine keeps running on a substituted default temperature, but the ECU no longer has real feedback from this sensor, so it should be diagnosed and repaired without delay.
Can I keep operating the machine with this code active?
The engine will continue to run since the ECU falls back to a default charge air cooler outlet temperature and tries to maintain normal operation. Because the ECU is working from an assumed value instead of a real sensor reading, it's best to get the fault diagnosed as soon as practical rather than run on it long term.
What's the difference between SPN 2630 FMI 4 and FMI 3?
Both are Warning-level codes describing a signal voltage that corresponds to a temperature outside what's physically possible, and they share nearly identical causes: bad terminals or connectors at the sensor or ECU, an open or short in the harness, a bad sensor, bad ECU software, or a bad ECU. FMI 4 specifically points to voltage that dropped below the sensor's low voltage specification, which some diagnostic listings group together with FMI 3 in the same troubleshooting sequence.
How is SPN 2630 FMI 4 different from the FMI 15 and FMI 16 high-temperature codes?
FMI 15 and FMI 16 describe the charge air cooler outlet temperature signal reading slightly or moderately high, meaning the ECU sees a plausible but elevated temperature value. FMI 4 is a signal-out-of-range low fault where the voltage itself is invalid and physically impossible, not just a high but believable temperature reading. If your symptom is an actual high air temperature reading rather than an invalid low-voltage signal, you're looking at the wrong code family.
What commonly causes this fault?
The most frequent culprits are a bad or corroded connector at the sensor or ECU, an open or shorted wire in the harness (including melted or pinched wiring), an intermittent short to ground, or a failed sensor. Less commonly, it traces back to bad or outdated ECU software or a faulty ECU.
Do I need a scan tool to diagnose this code?
A scan tool that can read the live sensor voltage and confirm the active fault status is very helpful, since it lets you verify whether the signal is genuinely out of range or check for other correlated engine fault codes. Basic electrical testing with a multimeter on the connectors, harness, and sensor covers most of the possible causes even without one.