PACCAR (Kenworth & Peterbilt)
PACCAR fault code
SPN 5848 / FMI 10
PACCAR Fault Code P3989: Exhaust Gas Temperature After SCR Catalyst – Internal Error
P3989 on PACCAR (Kenworth & Peterbilt) engines means: Exhaust Gas Temperature After SCR Catalyst – Internal Error. The failure mode (FMI 10) is “abnormal rate of change”.
Code details
- Manufacturer
- PACCAR (Kenworth & Peterbilt)
- Applies to
- PACCAR MX-13 (2017–2020)
- Fault code
- P3989
- J1939 SPN
- 5848
- FMI
- 10 — Abnormal rate of change
- Truck models in source
- Kenworth T680, T880, W900, T800; Peterbilt 579, 389, 567, 367
What to do next
- Read active and inactive codes with the OEM service tool and note the occurrence count.
- FMI 10 tells the shop the type of failure to test for: abnormal rate of change.
- Have a heavy-duty diesel technician confirm the fault against the engine or chassis service manual before replacing parts.
Get this code diagnosed
Send one request and nearby diesel shops and mobile mechanics can quote the repair.
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Related fault codes
- PACCAR Fault Code P3989 — PM Sensor – No Detection of Hot Exhaust Gasses
- PACCAR Fault Code P3989 — NH₃ Sensor – Value Not Changing When Expected
- PACCAR Fault Code P3811 — Heater Element PM Sensor – Voltage Too High or Short Circuit to Supply, Low Side
- PACCAR Fault Code P3815 — Heater Element PM Sensor – Voltage Too Low or Short Circuit to Ground, Low Side
- PACCAR Fault Code P3821 — Sensor Circuit PM Sensor – Voltage Too High or Short Circuit to Supply
- PACCAR Fault Code P3951 — CAN Communication – Timeout From DEF Quality Sensor
- PACCAR Fault Code P3955 — Exhaust Gas Temperature Before DOC – Data Valid But Too High
- PACCAR Fault Code P3962 — DEF Quality – DEF Concentration Too High
Source: PACCAR MX-13 2017–2020 fault code list (Diesel Laptops). See also OBD-II codes.