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Engine Oil Level – Data Valid but Above Normal Operational Range – Most Severe Level
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Overview
| CODE | REASON | EFFECT |
| Fault Code: 688 PID: P98 SPN: 98 FMI: 0 LAMP: Red SRT: |
Engine Oil Level – Data Valid but Above Normal Operational Range – Most Severe Level. High oil level has been detected by the oil level sensor. |
Possible low power, excessive smoke, oil dilution, contamination, or severe engine damage. The engine may derate. |
 ISB, ISC, and ISL with CM2150 – Engine Oil Level Sensor.
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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 688.
Component Location
The engine oil level sensor is located on the engine oil dipstick, on the air intake side of the engine. Refer to Procedure 100-002 (Engine Diagrams) in section E for further details on dipstick location.
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 using INSITE™ electronic service tool.
Shop Talk
Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.
Fault code 688 indicates that the oil level in the engine is much higher than the recommended oil level.
Other causes of fault code 688 may include:
- The engine may have been overfilled with oil during the most recent oil change.
- 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.
- The cooling system may be leaking into the lube oil system. Check for coolant in the oil.
Refer to Troubleshooting Fault Code t05-688
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