Here's what happened...i go do a little wheeling today for the first time since i installed the lift. It wouldnt let me go into 4lo, but 4hi worked fine. I checked all the wires, and everything looked fine. on a hunch i look at the tunercat program i tuned for my avalanche. I though i saw somewhere that turning off the PRNDL function under switches>calibration options would allow you to hold a gear to any RPM, which i wanted. I did notice that when i had it in neutral, the Neutral light was not showing being selected on the gauge cluster. so i reflashed the PCM with the PRNDL option checked, go to put in 4lo and everything worked fine. So i guess basically the computer didnt know that the tranny was in neutral or not so it wouldnt let it go into 4lo. What my question is...what exactly does the PRNDL option do? am i understanding it right? is there a glitch in the CATS program? I did notice that it messed with the door locks (dont know what it wsa doing exactly, but it locked unlocked more when put it in and out of gear) and when i first started up the truck, it revved up kinda high really fast for a split second with the PRNDL off. thanks for any help

Chad

 

I thgink thats there for people doing trans swaps with non electronic ones. this way the pcm is not looking for what gear its in.