Kenworth PACCAR MX-13 repair, fault codes & roadside
The PACCAR MX-13 in the Kenworth T680/T880 is the same 12.9L inline-six used across Peterbilt and DAF. Aftertreatment and EGR faults make up most of its roadside calls; the long block itself is durable.
Get a diesel tech on the truck — your engine and fault info ride along so they quote before you accept.
Common PACCAR MX-13 faults
- DPF differential-pressure and failed-regen faults
- DEF dosing and SCR conversion-efficiency faults
- EGR valve / EGR cooler and boost-control faults
- Coolant-temperature and oil-pressure protection events
Relevant fault codes (PACCAR MX-13)
These heavy-duty SPN/FMI codes commonly show up on engines like the PACCAR MX-13. Tap one for a plain-English meaning, severity, likely causes, and roadside first moves.
Roadside first moves
Note the exact SPN/FMI and any companion codes, read the freeze-frame data, and don't keep driving a derated truck — it can escalate to a no-start. When in doubt, look up your code and get a qualified mobile diesel tech on the PACCAR MX-13.
FAQ
The most common PACCAR MX-13 roadside faults are: DPF differential-pressure and failed-regen faults; DEF dosing and SCR conversion-efficiency faults; EGR valve / EGR cooler and boost-control faults.
Yes — most PACCAR MX-13 roadside issues are aftertreatment (DPF/DEF/SCR), EGR, boost, or electrical faults a mobile diesel tech can scan and often resolve on-site. Internal damage or a fully plugged DPF needs a shop.
Common heavy-duty SPN/FMI codes relevant to the PACCAR MX-13 include SPN 3251 FMI 2 (DPF Differential Pressure — Data Erratic); SPN 3361 FMI 7 (DEF Dosing Unit — Not Responding Properly); SPN 4364 FMI 18 (SCR Conversion Efficiency — Below Threshold); SPN 4094 FMI 31 (DEF Quality — Out of Spec). Look any of them up below.
Find a provider & related resources
General repair guidance for the Kenworth PACCAR MX-13. Not a substitute for a scan-tool diagnosis on your specific truck.