Reason for failure:
MIL Engine Off

Passed MIL Engine On test.

No codes when I used my scan tool.

What could cause this issue?

2000 Silverado 2500 6.0

 

Try cleaning the MAF. Lots of times its dirty or bad but wont show a code.

 

are u saying the check engine light bulb check failed?

 

I assume that is what it means. It failed when was key turned off, but the light worked when on. Seems like if the bulb needed to be replaced that it would not work either time. That test was a visual test.

 

not sure what you are describing.
proper operation is: the mil light should light up at key on, engine off, then go off with the engine running if no dtc are set.
if its not illuminating at key on the led in the cluster may be bad. someone with a good scan tool can do a bulb verifcation check.