PACCAR MX (2004 Emissions) Fault Code: P1234 Common Rail Pump Unit 2 – Short Circuit Between ECU (D420) Pin (A27) and Pin (A28)

SET CONDITIONS:
The PCI ECU (D420) detects a short circuit between ECU pin A27 and pin A28.

DIAGNOSTIC CONDITION:
This diagnostic runs continuously when the ignition is on.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive after the ignition has been switched off for at least 15 seconds and switched on again and the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
Malfunctioning of the common rail pump unit 2 (L093) or wiring

ADDITIONAL INFORMATION:
When this DTC is active:
1. The engine torque is reduced.
2. The engine runs in protection mode.
3. The maximum rail pressure is limited to 1300 bar.