Linda1

Took GMC Sierra 2004 1500 to mechanic to finally have valve cover gasket and knock sensor w/harness replaced. The check engine light has been on for years because of the knock sensor issue. Mechanic says they replaced the valve cover gasket and knock sensor. The check engine light is now off. However, this morning we noticed that the check engine light doesn't come on when you initially turn the key before actually starting it....nor does it come on during any of the engine starting process. So, we disconnected a sensor to force the light to come on....and it didn't. So the check engine light doesn't appear to work at all now (after staring at it for a decade!). WHY?

Elcamino (Mike), Yeah, I am thinking that you might be right because nothing else is having issues. The part that kinda sucks is this radio didn't make 2 years in my Sierra....installed 11/2019 and already bad....I guess I will order another one and see if that fixes the issue.

First, I am suspecting that maybe something went wrong in the radio....and that is the most obvious thing even though it's not but a few years old.... As for how old the battery in my truck is, not sure - although, all the dash and interior lights go out fine - just stuff related to the radio that has become a problem. The battery was disconnected because other work was being done and that was part of the process of fixing the other truck issues.

A few years back I changed the radio in my GMC Sierra 2004 to JVC (from factory). Recently disconnected battery ....now the steering wheel controls don't work for the radio nor does the radio turn off when the door is opened. No other changes were done that could have impacted the radio, rechecked all the connections on back of radio, nothing seems wrong yet this stuff still isn't working correctly - any ideas?