jeffhulsey16

I know this is supposed to be ls1 tech but i figured my truck was close enough...Ive been having problems with my 2003 GMC with a 4.8 and auto for a while now. I had to cut out the cats cuz they were blocking up #'s 2,6,8 cylinders. then my trans started slipping so i bought a rebuilt trans. After that i never got 1st to engage and overdrive takes a while to go. The trans guy thoguht it was the tps and its electronic (was reading 20% throttle when off) so i got another one, and it didnt help. He took the truck back and put on a new maf senser and is checking out the cylinoids today, and he said if that dont fix it he wants me to buy a new PCM which is around 200. I'm just a broke college kid and I dont even want the truck anymore, I want a ls1 camaro, so can someone tell me why i cant get first gear and it wont go into overdrive easily? Ive spent WAY too much money on this piece of JUNK!

tptransmission

First you need to acan it for codes. If you haven't already.

jeffhulsey16

there was a maf code but he bought another one and the other is the rear bank O2 sensers which will go off because there are no catalytic converters., so he checked the valve body today and the valve body are good. I'm not sure if its 4th or just the torque converter lockup. he took it to an auto electrical place and all they could say was its either the pcm or the trans. were going to try to "borrow" a computer form a salvage yard. (were both not sure that even this will work, but if it fixes the problem...if you know if we have to reprogram it that would help too.) He guesses if it comes down to it he will pull the trans and install it in another vehicle to see if its ok or put a different rebuilt trans in it to see if its my computer. I really would like to not have to buy another computer their too expensive for me right now...im new to this site so i dont know if you can private message me if you have any other Q? thanks so much for your help and i will post results so if it ever happens to anything you work on you will know what to do.

performabuilt

iTrader: (25)

With out the cats and O2 sensors I will bet its not a trans issue or a PCM problem but rather and engine missfire issue causing lockup not to work, If the PCM detects missfire it will disable lockup.

jeffhulsey16

ok...thanks I left a message on my trans guys phone number and i will see what he has to say. It really doesnt seem to have a missfire, it runs better without the cats (probably because they were clogged for so long) but i will see if i can buy the stock header y pipes and o2 sensor reletively cheap tomorrow at the chevy only salvage place, and if it doesnt work i will let you know.

jeffhulsey16

So, I talked to my trans guy and he said that its not got FIRST and OD, so he doesnt think its misfiring. because lockup does work not od. I guess the next thing to ask is, are pcms vin sensative? I can get one from a salvage yard but it will need reprogrammed from the dealer. The dealer says it may be vin sensative but they might be blowing smoke out of their asp. And even then they might not know cuz they are small town dealer. cant i just find one that has matching codes on it or something? When their on the assembly line dont they just plug the computer up and just let it go? If you have any other ideas please ask!!