PACCAR MX (2004 Emissions) Fault Code: P1644 PCI ECU 5V Sensor Supply – Voltage Too High or Short Circuit to Supply

PACCAR MX (2004 Emissions) Fault Code: P1644 PCI ECU 5V Sensor Supply – Voltage Too High or Short Circuit to Supply

SET CONDITIONS:
The PCI ECU (D420) detects that the internal ‘5V power supply 2’ voltage is too high.

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

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when 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:
Issues within the ‘5V power supply 2’ with:
1. Sensor wiring
2. Sensor malfunction

ADDITIONAL INFORMATION:
1. Various 5V engine sensors receive their power supply through one of the 5V power supply groups from the PCI ECU (D420).
2. When this DTC is active, all sensors connected to ‘5V power supply 2’ will be out of operation.