Cummins ISB CM850 (2003-06) Fault Code: 688 PID: 98 SPN: 98 FMI: 0 Engine Oil Level ? Data Valid But Above Normal Operational Range ? Most Severe Level. High oil level has been detected by the oil level sensor.

Fault code 688 indicates that the oil level in the engine is much higher than the recommended oil level.

Other causes:

1)The engine may have been overfilled with oil during the most recent oil change
2)The fuel system may be leaking into the lube oil system. (Check for fuel system faults or use fluorescent fuel system dye to identify leaks)
3)The cooling system may be leaking into the lube oil system. (Check for coolant in the oil).

On-Board Diagnostic (OBD) Information:

1)The ECM illuminates the appropriate amber or red fault lamp when the diagnostic runs and fails
2)The ECM turns off the appropriate fault lamp when the diagnostic runs and passes.

Possible repairs:

1)Remove the oil drain plug. Drain the oil immediately to be sure all the oil
2)Remove and replace the oil filter
3)Fill the lubricating oil pan with clean 15W-40 lubricating oil to the low level.