PACCAR MX (2004 Emissions) Fault Code: P2609 Grid Heater Relay – Current Too Low or Open Circuit on ECU (D420) Pin (C55)

SET CONDITIONS:
The PCI ECU (D420) detects an open circuit on pin C55.

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

CORRESPONDING OBD READINESS MONITOR:
None

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. The sensor or actuator signal wiring has an open circuit.
2. A malfunction of the sensor or actuator

ADDITIONAL INFORMATION:
Through pin C55 the PCI ECU determines the status of the grid heater relay