PACCAR MX (2004 Emissions) Fault Code: P3003 PCI ECU Power Supply – Data Valid but Too Low

PACCAR MX (2004 Emissions) Fault Code: P3003 PCI ECU Power Supply – Data Valid but Too Low

SET CONDITIONS:
The PCI ECU (D420) detects that the power supply has dropped to below 10 V.

DIAGNOSTIC CONDITION:
This diagnostic runs continuously after starting and running the engine.

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:
1. Alternator malfunctioning
2. PCI ECU power supply, check:
– Whether more ECUs on the vehicle detect incorrect power supply
– Battery voltage
– PCI ECU power supply

ADDITIONAL INFORMATION:
For this diagnostic, the PCI ECU monitors its power supply only during engine operation to detect a running voltage drain-down. It does not detect a cranking voltage drain-down.