PACCAR PX-8 CM2150 (2007-09) Fault Code: 556 (ISB/QSB3.3) PID: 101 SPN: 101 FMI: 0 Crankcase Pressure – Data Valid but Above Normal Operational Range – Most Severe Level.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM. Use the following procedure in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

Possible causes:

1)Crankcase ventilation filter needs to be replaced
2)Crankcase pressure sensor damage
3)Malfunctioning or misassembled closed crankcase ventilation valve
4)Frozen, plugged, or restricted crankcase ventilation hose
5)Plugged or restricted crankcase ventilation hose
6)Plugged or restricted crankcase ventilation oil drain tube or check valve
7)Plugged or restricted crankcase breather tube (rear engine-mounted crankcase ventilation filter)
8)High air intake restriction.

Depending on the breather system used, the crankcase ventilation filter will be located:

1)On top of the rocker lever cover, between the rocker lever cover and the crankcase ventilation filter cover, or
2)At the rear of the engine, encased in an external crankcase ventilation filter housing that mounts to the flywheel housing.

Both systems are closed crankcase breather systems, meaning the crankcase gases are vented into the intake system at the inlet to the turbocharger compressor.

It is important to check for plugged or restricted hoses, tubes, check valves, and filters in extreme cold ambient temperatures.

If Fault Code 556 becomes active due to a plugged filter before the maintenance interval is reached or the filter plugs frequently, see the Crankcase Gases (Blowby) Excessive troubleshooting symptom tree.

After Fault Code 556 occurs, it is important to check for progressive damage to the engine due to the high crankcase pressure. Check for oil leaking from gaskets and seats.

Possible repairs:

1)Replace the crankcase pressure sensor.
2)Replace the crankcase ventilation filter.
3)Replace the crankcase breather element.
4)Clean or replace the crankcase ventilation oil drain tubes, check valves, breather tubes, or oil separator.
5)Replace the crankcase ventilation filter.
6)Replace the damaged gasket, seal, or other component.