PACCAR MX (2004 Emissions) Fault Code: P0135 Lambda Sensor Heater – Current Too Low or Open Circuit on ECU (D420) Pin (C46)

SET CONDITIONS:
The PCI ECU (D420) detects a lower current than expected on the control circuit of the lambda sensor heater.

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

RESET CONDITION:
The DTC changes to inactive after the diagnostic runs and passes.

POSSIBLE CAUSES:
1. Open circuit in the lambda sensor wiring
2. Lambda sensor failure