Cummins ISB4.5 CM2150 Fault Code: 556 PID: 101 SPN: 101 FMI: 0 Crankcase Pressure – Data Valid But Above Normal Operating Range – Most Severe Level.

Circuit Description
The pressure inside the crankcase is measured by the crankcase pressure sensor. When the crankcase pressure sensor determines that the crankcase pressure is higher than normal, this fault code is logged.

Component Location
The crankcase pressure sensor is located near the crankcase ventilation filter.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the engine speed is greater than 500 rpm.

Conditions for Setting the Fault Codes
The ECM detects that the crankcase pressure is greater than a calibrated value.

Action Taken When the Fault Code is Active
-The ECM illuminates the red STOP ENGINE lamp when the crankcase pressure limit is exceeded.
-The engine torque output will be reduced to protect the engine from excessive crankcase pressure.

Conditions for Clearing the Fault Code
-To validate the repair, start the engine and let it idle for 1 minute.
-The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
-The ECM will turn off the red STOP ENGINE lamp after the diagnostic runs and passes.
-The “Reset All Faults” command in INSITE™ electronic service tool can be used to clear active and inactive faults.

Possible Causes
-Crankcase breather filter needs to be replaced
-Crankcase pressure sensor damage
-Plugged or restricted crankcase breather oil separator
-Plugged or restricted crankcase breather oil drain tube or check valve
-Plugged or restricted crankcase breather draft tube
-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.