Reason:
At Least One Unacknowledged Most Severe Fault – Condition Exists

Effect:
None on performance.

Circuit Description:
There is at least one unacknowledged severe fault in the system.

Component Location:
The reset button or switch location depends on the original equipment manufacturer (OEM). Refer to the OEM troubleshooting and repair manual for component location.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected a fault that has not set the lamp within a calibrated threshold.

Action Taken When the Fault Code is Active:
The ECM illuminates the red STOP ENGINE lamp immediately after the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
The ECM will turn off the red STOP ENGINE lamp immediately after the diagnostic runs and passes.

Shop Talk:
This fault code occurs as a result of other fault codes becoming active or inactive. Fault Code 2661 will remain active until reset by the operator. Fault Code 2661 is designed to latch onto other fault codes that have become active or have gone inactive. The light is an indicator that will remain lit to inform the operator that there has been a fault code generated. The fault has no effect on engine performance.

Possible Causes:
1) Inactive fault codes
2) Faulty ECM