PACCAR MX (2004 Emissions) Fault Code: P1726 Exhaust Gas Pressure Before Turbine – Response Too Slow, On Requested Pressure

PACCAR MX (2004 Emissions) Fault Code: P1726 Exhaust Gas Pressure Before Turbine – Response Too Slow, On Requested Pressure

SET CONDITIONS:
The PCI ECU (D420) detects a too slow response of the requested pressure before turbine value.

DIAGNOSTIC CONDITION:
MX-11:
This diagnostic runs when the engine is running in engine mode ‘SCR heating’ or ‘SCR super high efficiency’ and the engine speed is more than 1000rpm during normal engine load conditions.

MX-13:
This diagnostic runs when the engine is running in engine mode ‘SCR super high efficiency’ and the engine speed is more than 1000rpm during normal engine load conditions.’

CORRESPONDING OBD READINESS MONITOR:
VTG monitor

RESET CONDITION:
This DTC will change to inactive after the ignition is keyed off and on again and the diagnostic runs and passes.

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. Exhaust gas leakage
2. Incorrectly calibrated VTG turbocharger actuator
3. Plugging of the pressure sensor before turbine pipe
4. Leaking BPV valve
5. Leaking EGR valve
6. Faulty VTG turbocharger nozzle ring mechanism or actuator
7. Faulty pressure sensor before turbine

ADDITIONAL INFORMATION:
1. The pressure before turbine is an input value for the engine management system and is used for control of the VTG, BPV valve and EGR valve.
2. The pressure is measured by the pressure sensor before turbine (F826).
3. This DTC is used to check the response time of the VTG, BPV and EGR valves based on the measured pressure before turbine.
4. DTC P1726 is an OBD fault. The corresponding OBD readiness monitor changes to ready once the diagnostics have run.

IMPORTANT: In an attempt the solve VTG turbocharger actuator position related DTCs, turbocharger actuators are occasionally recalibrated by the technician. By doing so, the actuator can be mistakenly calibrated to a smaller span than the initial maximum span of the turbocharger mechanism. In that case, the expected pressure before turbine is not reached during engine load situations, resulting in DTC P1726.