PACCAR MX (2004 Emissions) Fault Code: P1133 Lambda Sensor Heater – Voltage Too High or Short Circuit to Supply on ECU (D420) Pin (C46)

SET CONDITIONS:
This DTC is set when the ECU detects a higher voltage than expected on the signal or control circuit of the ECU.

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. The sensor or actuator signal wiring has a short circuit to supply.
2. A malfunction of the sensor or actuator