2001 tahoe thought 230k fully loaded. Was a friend's now is mine, very very little known history on it. It ran fine for months after it was bought then out of nowhere started to stall. Here's what it will do Start up fine, idle fine, run fine.. Gets up to temp. Starts running rough and stalls and doesn't want to start again until cooled down some. NO codes thrown or saved. I have done the back of the engine ground trick, it seemed like it helped actually. But then began acting up again. Last time I tried fixing on her I had my scanner plugged in and got it to throw P1635 & P1639. The 5V reference circuit(s) The only real lead I have going forward with this is that the clutch assembly on the AC started kicking on and off right as it started acting up and throwing the codes. Anyone else had anything like this and a good place to start checking?