PACCAR MX (2004 Emissions) Fault Code: P104B Inlet Air Pressure in Inlet Manifold – Data Valid but Too High

PACCAR MX (2004 Emissions) Fault Code: P104B Inlet Air Pressure in Inlet Manifold – Data Valid but Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the measured boost pressure is more than 0.5 bar [7.3 psi] higher 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. Turbo speed sensor malfunction
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).
3. The turbo speed sensor signal is used to calculate the expected boost pressure.