PACCAR (Kenworth & Peterbilt)
PACCAR fault code
SPN 3663 / FMI 6
PACCAR Fault Code P1234: Common Rail Pump Unit 2 – Short Circuit Between ECU (D420) Pin (A27) and Pin (A28)
P1234 on PACCAR (Kenworth & Peterbilt) engines means: Common Rail Pump Unit 2 – Short Circuit Between ECU (D420) Pin (A27) and Pin (A28). The failure mode (FMI 6) is “current above normal or grounded circuit”.
Code details
- Manufacturer
- PACCAR (Kenworth & Peterbilt)
- Applies to
- PACCAR MX-13 (2017–2020)
- Fault code
- P1234
- J1939 SPN
- 3663
- FMI
- 6 — Current above normal or grounded circuit
- 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 6 tells the shop the type of failure to test for: current above normal or grounded circuit.
- 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 P0205 — Common Rail Pump Unit 2 – Current Too Low or Open Circuit on ECU (D420) Pin (A27) or Pin (A28)
- PACCAR Fault Code P0273 — Common Rail Pump Unit 2 – Voltage Too Low or Short Circuit to Ground on ECU (D420) Pin (A28)
- PACCAR Fault Code P0274 — Common Rail Pump Unit 2 – Voltage Too High or Short Circuit to Supply on ECU (D420) Pin (A28)
- International Fault Code SPN 3663 FMI 4 — Injector 5 Close Coil – Short Circuit
- International Fault Code SPN 3663 FMI 5 — Injector 5 Close Coil – Open Circuit
Source: PACCAR MX-13 2017–2020 fault code list (Diesel Laptops). See also OBD-II codes.