PACCAR PX-8 CM2150 (2007-09) Fault Code: 1981 PID: SID 324 SPN: 3926 FMI: 0 Aftertreatment Particulate Filter Differential Pressure – Data Valid but Above Normal Operational Range – Least Severe Level. The aftertreatment differential pressure has exceeded the maximum operating limits or the diesel particulate filter is plugged.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable changes to the calibration stored in the ECM. If necessary, calibrate the ECM.

An engine torque derate for extended EGR valve closed operation exists for this fault code. The engine torque derate for extended EGR valve closed operation operates on a time based system. The time based system will count up anytime a fault code that closes the EGR valve is active. Once the timer reaches 20 hours, an engine torque derate of approximately 15 percent will be applied.

The engine torque derate will be removed as soon as the fault code goes inactive, and the timer will begin to count down. If the fault code reoccurs within the next 20 hours of engine operation, the engine torque derate will immediately be applied, and the timer will then reset to 20 hours. The engine must operate for 20 hours with no active faults that close the EGR valve, for the timer to clear. After the timer has cleared, the engine must then operate for another 20 hours, with an active fault code that closes the EGR valve to apply the derate.

This fault code indicates that the soot load inside the aftertreatment diesel particulate filter has reached the maximum level, soot level stage 4. Regeneration of the aftertreatment diesel particulate filter at this stage is not possible. The aftertreatment diesel particulate filter must be inspected. If it meets the inspection criteria, it can be cleaned using an SPX air pulse cleaning machine (or equivalent). If it does not meet the inspection criteria, it must be replaced.

Possible causes:

1)The aftertreatment diesel particulate filter can be plugged with soot.
2)The engine has been operating in light load conditions that prevent exhaust temperatures from being high enough to actively regenerate the aftertreatment particulate filter.
3)The aftertreatment wiring harness connectors could be connected to the wrong aftertreatment exhaust gas temperature sensors.
4)The aftertreatment wiring harness or aftertreatment exhaust gas temperature sensor connector pin installation could be incorrect.
5)The aftertreatment diesel particulate filter differential pressure sensor has malfunctioned.
6)The aftertreatment diesel particulate filter may have reached the ash cleaning interval.
7)The aftertreatment diesel particulate filter can accumulate an excessive amount of ash in a short time period, due to excessive oil consumption or due to non-combustible elements such as, but not limited to, iron, potassium, or calcium contained in the fuel supply or additives.
8)An engine malfunction that is elevating the engine smoke output.

Possible repairs:

1)Replace the aftertreatment diesel particulate filter.
2)Replace the diesel oxidation catalyst.
3)If no short circuit is found, replace the aftertreatment diesel particulate filter differential pressure sensor.
4)Replace the aftertreatment diesel particulate filter.
5)Replace the diesel oxidation catalyst.
6)Calibrate the ECM with the calibration containing corrections to resolve Fault Code 1981.
7)Replace the six injectors.
8)If necessary, calibrate the ECM.