PACCAR MX (2004 Emissions) Fault Code: P1711 NOx Concentration Before Catalyst – Data Valid but Too High

PACCAR MX (2004 Emissions) Fault Code: P1711 NOx Concentration Before Catalyst – Data Valid but Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the measured engine NOx emissions are higher than the expected engine NOx emissions for more than 40 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs:
1. When the engine is running at a steady load and its speed is between 1050 and 1850 rpm and
2. When the coolant temperature is above 50°C [122°F] and
3. The engine mode is SCR high efficiency or standard or protection and
4. 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.

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:
1. The end-stops of the VTG turbocharger actuator are not calibrated correctly.

IMPORTANT: In an attempt the solve VTG turbocharger actuator position related DTCs, turbocharger actuators are occasionally recalibrated by a technician.

By doing so, the actuator is mistakenly calibrated to a smaller span than the initial maximum span of the turbocharger mechanism.

In that case the requested pressure before turbine cannot be reached, resulting in a too low flow of EGR gas and a too high engine-out NOx level.

2. Diesel fuel used is not in accordance with EN590
3. Leakage in inlet air system
4. Clogged EGR pressure difference sensor venturi
5. Humidity sensor deviation
6. NOx sensor before catalyst deviation

ADDITIONAL INFORMATION:
1. The measured engine NOx emission is compared with the expected engine NOx emission.
2. The engine NOx emissions are measured by the NOx sensor before catalyst (F844).