PACCAR MX (2004 Emissions) Fault Code: P1206 Injector Solenoid Valve Cylinder 5 – Short Circuit Between ECU (D420) Pin (A3) and Pin (A4)

SET CONDITIONS:
The PCI ECU (D420) detects a short circuit between the ECU pin A3 and A4 circuits.

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

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected. To enable the injector output, the DTCs must be cleared.

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. Faulty injector
2. Engine wiring harness

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