Where in the heck did my start sense go??

[Matahoe]

Hello everyone. Just recently noticed an issue with my 2005 Tahoe that doesn't seem right.

I previously owned a 2005 GMC Canyon and a 2006 GMC Envoy. Both vehicles had the automatic crank/start sense feature. All you had to do was bump the key to start and release and the engine would continue to crank until it detected that the engine was started. I dont seem to have that feature but all the literature I have read seems to indicate otherwise. Can one of you electronics gurus set the record straight? Is this a feature that wasn't in our year models? Thanks!

 

[M1Gunner]

Here’s your answer brother

 

[Matahoe]

So if I am reading this diagram right. When I release the key there should still be power to the PCM controlled side of the starter relay. OK got it. Looks like it may be an ignition switch issue. I should be able to probe the pink wire and see if there is 12 volts when I release the key in run. Thanks.

 

[Matahoe]

I had the PCM controlled crank feature tested today and frankly with the results I am a more confounded than ever. Maybe someone can help out here?

So what I did was I pulled the fuel pump relay. I then held the key in crank for well over .4 seconds. .4 seconds is the time the service manual says you need to wait in order for the PCM to take control of the crank. However while testing this and letting the key go back to run the engine won't continue to crank like it should. It almost seems as if the PCM isn't getting the signal from the engine that it is running or missing a tach signal or something.

Hmm. I had a remote starter installed a few years ago but had it removed. I wonder if there is a bypass module still left over screwing up the ignition somehow.

Does anyone have a pinout diagram for the ignition switch or its connector? I need to see what specific circuits are passing through the switch other than 12 volt constant/crank/ignition 1 and 2, etc.