PACCAR MX (2004 Emissions) Fault Code: P170F NOx Concentration Before Catalyst – Data Valid but Too High During Overrun

PACCAR MX (2004 Emissions) Fault Code: P170F NOx Concentration Before Catalyst – Data Valid but Too High During Overrun

SET CONDITIONS:
The PCI ECU (D420) detects that the measured engine NOx emissions are too high for a fuel injection cutout situation for more than 21 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs:
1. During coasting (no fuel injection) and
2. When the coolant temperature is above 50°C [122°F] and
3. The NOx sensor before catalyst (F844) is in the operating mode

CORRESPONDING OBD READINESS MONITOR:
Exhaust gas sensors monitor

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

IMPORTANT:
1. For Eaton Ultrashift transmissions, idle drop can only go to 1000 rpm.
2. For Alison Autoshift transmissions, it is not possible to conduct this test.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the following conditions:
– Corresponding readiness monitor displays ‘Ready’
– Diagnostic conditions are met
– Set conditions are met
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
NOx sensor before catalyst deviation

ADDITIONAL INFORMATION:
1. The measured engine NOx emissions are compared with the expected engine NOx emissions while coasting (fuel injection cutout).
2. The engine NOx emissions are measured by the NOx sensor before catalyst (F844).