PACCAR MX (2004 Emissions) Fault Code: P1221 Injector Solenoid Valve Cylinder 4 – Current Too Low or Open Circuit on ECU (D420) Pin (A11) and or Pin (A12)

PACCAR MX (2004 Emissions) Fault Code: P1221 Injector Solenoid Valve Cylinder 4 – Current Too Low or Open Circuit on ECU (D420) Pin (A11) and or Pin (A12)

SET CONDITIONS:
The PCI ECU (D420) detects no or a too low current in the electrical circuit of the injector.

DIAGNOSTIC CONDITION:
This diagnostic runs when the engine is running.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
1. This DTC changes to inactive when the fault is no longer detected.
2. To enable the injector output, the ignition must be shut off for more the 15 seconds and turned on again.

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:
1. Open circuit in the wiring of the wiring loom frame (valve cover)
2. Faulty injector
3. Engine wiring harness

ADDITIONAL INFORMATION:
The injector output is disabled by the PCI ECU when this DTC is detected.