PACCAR PX-8 CM2150 (2007-09) Fault Code: 556 (ISC/ISL) 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 breather filter needs to be replaced
2)Crankcase pressure sensor damage
3)Plugged or restricted crankcase breather oil separator
4)Plugged or restricted crankcase breather oil drain tube or check valve
5)Plugged or restricted crankcase breather draft tube
6)Frozen, plugged, or restricted crankcase breather tube.

It is important to check for plugged or restricted hoses, tubes, check valves, oil separator, 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 seals.

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.