So... I have been fighting trying to get my 04 LQ9 to run properly. Have aftermarket stand alone harness and computer. Motor will start..stumble and die. If I put my foot on the gas pedal it will run, rev up, and if you hold your foot on the gas pedal it will run for as long as you want. take your foot off the gas and it stumbles and stalls.
So I was doing a heat cycle figuring that maybe it needs to "learn". Because sometimes it will run for 15-20 seconds stumbling around 300 rpm. I had my scanner plugged in watching the values as I was bringing it up to temp. AS SOON AS THE COMPUTER TRIED TO TURN THE FANS ON, at 196, the stft went crazy into the negatives (-15-25) and threw a running rich code on both banks?

IDEAS??????

 

Unplug the CTS and try again
Ohm the injectors
Check for vacuum leaks

 

CTS is working fine,
tried a whole new set of injectors
checked multiple times for vacuum leaks, no sign of any, not even in the MAP sensor

 

ground circuit for your fans...is it on same circuit as o2 sensors? Redundant grounds ..

 

I am not sure of the answer to this. The computer is the ground wire for the relay I use for the fan. fan independently grounded.

 

Anybody?????

 

Are you doing test runs with the alternator disconnected? I have my 5.3 on a test stand running on battery only and it's doing the same thing your is. The only code that I'm getting that isn't expected is P0343 - Camshaft Position Sensor Circuit High Input. I did some research and it looks like this can be caused by low battery voltage.

 

I have tried it both ways, but havent run it all the way up to temperature just on battery. still wont idle either way