08 tahoe hybrid. The check engine light does not illuminate at start-up, when there is an mil present, or any other time. I also have the associated pid for malfunction indicator circuit failure. I don't see any blown fuses. Also, I think all the 12v acc plugs work (2 in front, 1 inside center console, 1 behind center console by the rear hvac / radio controls).

does anyone know exactly what fuse protects the check engine light? Has anyone ever had this happen? Anyone know the most common cause other than a fuse or the led itself? And does anyone have the circuit diagram?


thanks all

 

Does your Onstar work, on the rear view mirror? or the ambient temperature gauge on the dash? Believe it or not the CEL is somehow connected to these. There is a fuse under the hood that is not even close to being marked correctly that is connected to these.
My rear view mirror plug had a short and I had these symptoms. Unfortunately neither the fuse guide in my owners manual nor the under hood fuse map is even remotely close to reality for my Hybrid, I guess they didn't bother to change it from the regular Tahoe.(at least on mine) I literally had to pull every fuse to find the right one and nothing was marked any way that would make any sense. I don't recall which fuse it is, but it is under the hood.

 

Yes, the On-star works (though I never used it, but I did press the button to check it), as does the rearview mirror and the thermometer. I checked all the fused with a 12v light for what that's worth. Maybe I should try pulling every one. Thank you very much for the reply.

 

The CEL is hard wired directly to the engine computer. Either it is not grounded, doubt that, or the computer stopped doing its job.

 

I am still able to scan the odb and pull codes as well as freeze frame data, etc. Also checked every fuse with none blown. Any idea on the pinout for the cluster connector? In particular which pins should illuminate the check engine light?

 

No I don't know which pin it is.

 

LED or bulb inop?