John Deere Engines SPN2659FMI15 Fault Code: EGR Flow Signal Slightly High
Also called Calculated EGR Flow Rate Slightly High, EGR Flow Signal Moderately High, Engine Shutdown Commanded by Application
EGR Flow Signal Slightly High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 2659 FMI 15 sets when the ECU calculates or measures EGR flow while the EGR valve is commanded closed. There is no separate physical EGR flow sensor on some engines; flow is inferred from the difference between intake manifold air temperature and charge air cooler outlet temperature, or measured by a differential pressure EGR flow sensor on others. The alarm level is a Warning, and the ECU responds by running the EGR/VGT system in open loop mode, or in some versions, by derating the engine.
Medium severity. This code is logged as a Warning and the engine keeps running. Depending on which version of the diagnostic logic your engine uses, the ECU may only switch the EGR/VGT system to open loop control, or it may derate engine power. Either way it should be diagnosed the same shift since the underlying sensor or valve fault can worsen or trigger related codes.
What does John Deere Engines error code SPN2659FMI15 mean?
SPN 2659 FMI 15 means the engine control unit thinks exhaust gas is flowing through the EGR system at a time when the EGR valve is supposed to be fully closed, so no flow should be present. Depending on the engine and software version, this flow value is either calculated from a difference between intake manifold air temperature and charge air cooler outlet temperature, or it is measured more directly by a differential pressure EGR flow sensor combined with a temperature based model.
Because there is often no dedicated EGR flow sensor, this code can be a real EGR valve problem (stuck open, worn seals, leaking O-rings) or it can be a false alarm caused by a bad reading from one of the temperature sensors feeding the calculation. That is an important distinction for troubleshooting: you are chasing either a mechanical valve issue or a sensor/wiring issue that is tricking the ECU.
Once the code is active, the ECU no longer trusts the EGR/VGT closed-loop control and switches to open loop operation for that system, or in some configurations, derates the engine to protect it. Either response is the ECU's way of saying it cannot verify EGR flow is behaving as commanded.
What triggers a John Deere Engines SPN2659FMI15 code?
The code sets while the engine is running and the fault condition is active: the ECU detects EGR flow occurring at a time when the EGR valve is closed. On versions using a differential pressure EGR flow sensor, the code sets when EGR flow is detected by that sensor and its temperature based model while the valve is commanded closed. No specific voltage, pressure, or time threshold is given.
Common causes of SPN2659FMI15
- Bad or corroded sensor connectors (including CACOT or MAT sensor connectors that have been swapped with each other)
- High resistance, open circuit, or short to signal wire in the sensor or ECU wiring harness
- Bad charge air cooler outlet temperature (CACOT) sensor
- Bad intake manifold air temperature (MAT) sensor
- Bad EGR temperature sensor or its connector
- Bad EGR flow sensor or its connector (differential pressure style)
- Bad ECU connector connection
- Outdated or bad ECU software
- Bad ECU
- Clogged EGR valve, leaking or damaged O-rings, or a stuck EGR valve
- Bad EGR valve
- Intake and exhaust passages restricted or damaged
- Other active codes on related SPNs (2791, 105, 412, 2630, 27) that should be resolved first
How to troubleshoot John Deere Engines SPN2659FMI15: first checks
- Check for and resolve any other active DTCs first, especially those tied to SPN 2791, SPN 105, SPN 412, SPN 2630, or SPN 27; these are listed ahead of SPN 2659 FMI 15 in the recommended troubleshooting sequence and can cause this code to set falsely
- Inspect the CACOT sensor and MAT sensor connectors closely; on some engines these connectors can be physically swapped with each other, which will cause this fault
- Visually inspect all EGR related sensor and ECU connectors for corrosion, bent pins, or loose terminals
- Check wiring harness runs to the MAT sensor, CACOT sensor, EGR temperature sensor, and EGR flow sensor for chafing, open circuits, shorts to signal wire, or high resistance connections
- Physically inspect the EGR valve for sticking, clogging, or leaking or damaged O-rings, and confirm it moves and seats fully closed
- Inspect intake and exhaust passages for restriction or physical damage that could skew the flow calculation
- Confirm ECU software is up to date, since outdated software is a listed cause
How the code clears
No separate clearing step is listed. Once the root cause (sensor, connector, wiring, valve, or software) is repaired and the engine is run through a normal cycle, the code should stop reoccurring. If it persists after these repairs, ECU replacement may be needed, but that should be a last step after all sensors, connectors, wiring, and the EGR valve have been verified good.
Frequently asked questions
What does John Deere SPN 2659 FMI 15 mean?
It means the ECU has detected or calculated exhaust gas recirculation (EGR) flow at a time when the EGR valve should be fully closed and no flow should exist. It is logged as a Warning.
Will SPN 2659 FMI 15 shut down my engine?
Not directly. The alarm level is Warning. Depending on the software version, the ECU either runs the EGR/VGT system in open loop mode or derates the engine, but it does not command an immediate shutdown for this specific code.
Is there a physical EGR flow sensor on my engine?
On some engine software versions, no. Flow is calculated from the difference between intake manifold air temperature and charge air cooler outlet temperature. On other versions, an EGR flow sensor makes a differential pressure measurement combined with a temperature based model.
Can a bad sensor cause this code even if the EGR valve is fine?
Yes. Since flow is often inferred rather than directly measured, a false reading from the intake manifold air temperature sensor or the charge air cooler outlet temperature sensor can trigger this code even with a healthy EGR valve.
Why do the MAT and CACOT sensor connectors matter?
On some engines these two connectors can be accidentally swapped during service, which feeds the ECU incorrect temperature data and can falsely trigger SPN 2659 FMI 15.
What should I check before replacing the ECU?
Work through sensor connectors, wiring for opens/shorts/high resistance, the MAT, CACOT, and EGR temperature or flow sensors, and the EGR valve itself, including O-rings and passage restrictions. ECU software and the ECU are listed as possible causes but should be checked last.
Are there other codes I should check first?
Yes. The troubleshooting sequence lists any active DTCs with SPN 2791, SPN 105, SPN 412, SPN 2630, or SPN 27 as items to resolve before focusing on SPN 2659 FMI 15.