Cummins ISB CM850 (2003-06) Fault Code: 234 (Marine) PID: 190 SPN: 190 FMI: 0 Engine Crankshaft Speed/Position – Data Valid but Above Normal Operational Range – Most Severe Level. Engine speed signal indicates engine speed above engine protection limit.

Possible causes:

1)External fuel sources drawn into the intake air passage
2)Reverse powering (motoring) of the engine
3)Tampering of the engine speed/position sensors.

Inspect the intake manifold for sources of flammable vapors. Check the turbocharger seals to verify that there are no oil leaks. Inspect the engine speed/position sensors for damage or tampering.

Possible repairs:

1)Replace the crankshaft engine speed sensor.
2)Replace the camshaft engine position sensor.
3)Replace the ECM.