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.

Posted by PerDiezel Solutions on January 18, 2026

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.

Cummins ISB CM850 (2003-06) Fault Code: 687 (ISC) PID: 103 SPN: 103 FMI: 1 Turbocharger Number 1 Speed Low – Data Valid but Below Normal Operational Range – Moderately Severe Level. Low turbocharger speed detected by the ECM.

Cummins ISB CM850 (2003-06) Fault Code: 687 (ISB) PID: 103 SPN: 103 FMI: 18 Turbocharger number 1 speed low – warning level. Low turbocharger speed detected by the ECM.

Cummins ISB CM850 (2003-06) Fault Code: 649 PID: SID 153 SPN: 1378 FMI: 11 Change Lubricating Oil and Filter – Condition Exists. Change engine oil and filter.

Cummins ISB CM850 (2003-06) Fault Code: 599 PID: SID 25 SPN: 640 FMI: 14 Auxiliary Commanded Dual Output Shutdown – Special Instructions. The engine protection limit has been exceeded for the dual outputs calibrated limits.

Cummins ISB CM850 (2003-06) Fault Code: 598 PID: 167 SPN: 167 FMI: 11 Electrical Charging System Voltage Low – Data Valid But Below Normal Operating Range – Most Severe Level. Very low battery voltage detected by the battery voltage monitor feature.

Cummins ISB CM850 (2003-06) Fault Code: 597 PID: 167 SPN: 167 FMI: 1 Electrical Charging System Voltage Low – Data Valid But Below Normal Operating Range – Moderately Severe Level. Low battery voltage detected by the battery voltage monitor feature.

WARNING!