Cummins ISB4.5 CM2150 Fault Code: 688 PID: SPN: 98 FMI: 0 Engine Oil Level – Data Valid but Above Normal Operating Range – Most Severe Level.

Posted by PerDiezel Solutions on January 20, 2026

Circuit Description
An algorithm in the electronic control module (ECM) calibration monitors engine oil level while the ECM is keyed on and no engine speed is detected. If the engine oil level exceeds a certain threshold, the ECM will activate Fault Code 688.

Component Location
The engine oil level sensor is located on the engine oil dipstick, on the left side of the engine.

Conditions for Running the Diagnostics
This diagnostic runs when the keyswitch is in the ON position and the engine speed is 0 rpm.

Conditions for Setting the Fault Codes
The engine oil level is detected to be above the normal operating level at key-on.

Action Taken When the Fault Code is Active
-The ECM illuminates the red STOP ENGINE light immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code
-The ECM will turn off the red STOP ENGINE light and the fault code state will become inactive immediately after the diagnostic runs and passes.
-The fault code can also be cleared with INSITE™ electronic service tool.

Possible Causes
-The engine may have been overfilled with oil during the most recent oil change.
-The fuel system may be leaking into the lubricating oil system. Check for fuel system faults or use fluorescent fuel system dye to identify leaks.
-The cooling system may be leaking into the lubricating oil system. Check for coolant in the oil.

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Cummins ISB4.5 CM2150 Fault Code: 649 PID: SID 115 SPN: 1378 FMI: 11 Engine Oil Change Interval – Condition Exists.

Cummins ISB4.5 CM2150 Fault Code: 598 PID: 167 SPN: 167 FMI: 1 Electrical Charging System Voltage – Data Valid But Below Normal Operating Range – Most Severe Level.

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WARNING!