Code Details
| Display code | SPN 1569 FMI 31 |
|---|---|
| SPN | 1569 |
| FMI | 31 |
| OEM code | None listed |
| Manufacturer | PACCAR |
| System | Engine �?engine protection / derate control |
| Component | Engine control module / derate arbitration |
| Source address | Unknown or not applicable |
| Severity | high |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-11 |
Plain-English Meaning
The MX-11 ECM deliberately limits engine power or torque when it detects a condition that could cause damage or emissions non-compliance. SPN 1569 FMI 31 itself is not the root problem �?it is the engine telling the driver that power has been reduced because of a different active fault. Identify and fix that underlying fault to restore full power. On Kenworth T270, T370, and Peterbilt 220, 330 trucks with the PACCAR MX-11, the SCR inducement counter behaves identically to the MX-13. DAVIE4 and PACCAR ESA display the inducement status and remaining counter distance. The MX-11 is commonly paired with Allison automatic transmissions on Class 7 vocational applications, and the J1939 network fault history in DAVIE4 is important for ruling out an unrelated J1939 communication fault that may have triggered a false aftertreatment fault. After resolving the root cause, the DAVIE4 inducement reset procedure clears the derate.
SPN 1569 FMI 31 is Engine Derate Request from ECM. FMI 31 is used as a condition exists or event flag. On PACCAR MX-11 engines (used in Kenworth T680 and Peterbilt 579), DAVIE4 diagnostic software can display the derate level, the reason code driving the derate, and all other active faults. JPRO Fleet Management can also read this fault and display the triggering condition.
Common Symptoms
- Reduced engine power or torque during operation
- Check engine lamp active
- Other active fault codes present alongside SPN 1569
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Aftertreatment system fault triggering emissions derate (SCR efficiency, DEF quality, DPF pressure)
- Engine protection derate from oil pressure, coolant temperature, or boost fault
- Transmission protection event requesting engine derate
- Aftertreatment inducement active due to emissions non-compliance
First Checks
- Connect DAVIE4 or JPRO and review all active faults �?SPN 1569 FMI 31 will be accompanied by the root cause fault
- Identify the fault category (aftertreatment, engine protection, transmission) to prioritize diagnosis
- Address the root cause fault; the derate will clear when the triggering condition is resolved
- Connect DAVIE4 and identify all active fault codes contributing to the MX-11 SPN 1569 inducement
- Check J1939 fault history for unrelated network faults that may have confused aftertreatment reporting
Can I Keep Driving?
Power is limited. Safe to limp to a service facility but do not continue heavy-load operation until the root cause is identified and resolved.
Related Codes
Related Lookup Pages
Sources
- PACCAR / Kenworth / Peterbilt Service Support — MX Engine Resources PACCAR Inc. · oem · accessed 2026-06-11 · confidence medium
Source: PACCAR Inc., PACCAR / Kenworth / Peterbilt Service Support — MX Engine Resources. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - PACCAR Engine Technical Services PACCAR Inc. · oem · accessed 2026-06-10 · confidence medium
Source: PACCAR Inc., PACCAR Engine Technical Services. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - 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
FAQ
Is SPN 1569 FMI 31 specific to the PACCAR MX-11 or does it appear on other engines?
SPN 1569 FMI 31 is a SAE J1939 standard fault code used across many heavy-duty engine platforms to indicate an active engine derate. It is not MX-11 specific �?the same SPN 1569 FMI 31 appears on Cummins, Detroit, Volvo, and Mack engines. The diagnostic approach (find the root cause fault that triggered the derate) is the same across all platforms.
Can the PACCAR MX-11 derate be reset without fixing the root cause?
Clearing fault codes without fixing the root cause will temporarily remove the code, but the derate will return once the ECM re-evaluates the fault condition. Repeated clearing without repair is not recommended. On some platforms, the derate level escalates with repeated emissions fault occurrences, making continued clearance without repair increasingly counterproductive.
What is the typical derate level for SPN 1569 FMI 31 on the MX-11?
The derate level depends on the triggering fault and the number of regeneration or compliance opportunities that have been missed. Early-stage derates may be 25�?0% power reduction. More advanced inducement stages can limit speed to 55 mph or impose idle-only operation. DAVIE4 displays the current derate level and the reason code so the technician can determine the inducement stage.