PACCAR MX (2004 Emissions) Fault Code: P1128 Inlet Air Temperature In Inlet Manifold – Data Valid but Too High

PACCAR MX (2004 Emissions) Fault Code: P1128 Inlet Air Temperature In Inlet Manifold – Data Valid but Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the inlet air temperature is above 125?C [257?F].

DIAGNOSTIC CONDITION:
The diagnostic starts to run 30 seconds after the engine is started.

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?
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Contaminated intercooler
2. Faulty engine cooling fan
3. Boost temperature sensor deviation

ADDITIONAL INFORMATION:
1. The inlet air temperature is measured in the inlet manifold near cylinder 2 by the boost temperature sensor (F804).

2. When this DTC is active:
– The engine runs in protection mode
– DPF regeneration is disabled