PACCAR MX (2004 Emissions) Fault Code: U1074 Inlet Air Temperature Before Compressor – Data Erratic, Intermittent or Incorrect

PACCAR MX (2004 Emissions) Fault Code: U1074 Inlet Air Temperature Before Compressor – Data Erratic, Intermittent or Incorrect

SET CONDITIONS:
The PCI ECU (D420) receives a CAN message from the humidity sensor (F852) that contains an out-of-range value for the temperature.

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

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive after the ignition is keyed off for at least 15 seconds and keyed on again, and 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. E-CAN communication
2. Faulty humidity sensor

ADDITIONAL INFORMATION:
The humidity sensor is a smart sensor that communicates with the PCI ECU via E-CAN. The sensor measures the following three properties of the drawn in pre-compressor (VTG turbo charger) air in the inlet air pipe:
1. Relative humidity
2. Pressure
3. Temperature