Hello everyone,
I have a Pontiac Bonneville 1992 that used to make 22 MPG. Lately, it dropped down to 10-12 MPG. I took my car to AutoZone to check the engine with DCT – diagnostic code testing- buy the guy could not do it because the check engine light was not working at all – even when you start the engine- . Any idea about the problem.
Thanks a lot

Burnt bulb.

If it's not coming on during the bulb check (ignition on, car not running) then the bulb is the most likely thing.

My friend had a similar problem....no check engine light....after he opened the cluster he found out the bulb was removed..... the car was bought used and we assume it was removed by the previous owner