PACCAR MX (2004 Emissions) Fault Code: P104C Inlet Air Pressure in Inlet Manifold – Data Valid but Too Low

PACCAR MX (2004 Emissions) Fault Code: P104C Inlet Air Pressure in Inlet Manifold – Data Valid but Too Low

SET CONDITIONS:
The PCI ECU (D420) detects that the measured boost pressure is more than 0.5 bar [7.3 psi] lower than the expected boost pressure for more than 50 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs:
1. when the engine is running at a steady load, and
2. when the coolant temperature is above 50°C [122°F], and
3. when ambient temperature is between -15 and 40°C [5 and 104°F], and;
4. The engine mode is SCR high efficiency or standard.

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? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Leaking inlet air system
2. Boost pressure sensor deviation
3. Humidity sensor deviation
4. Turbocharger failure

ADDITIONAL INFORMATION:
1. The measured boost pressure is compared with an expected boost pressure.
2. The boost pressure is measured by the boost pressure sensor (F802).