So I’ve got a 99 Yukon here at work with the 4 button 4 wheel drive. The truck basically shifts into 4th gear at like 10mph and almost stalls the truck. 4 wheel drive buttons are all lit up including the N and service 4wd on the dash. If I pull the fuses for the 4wd the truck will drive perfect in 2wd.
So I replaced the switch 1st put the fuses in and it seemed that all was fixed. Truck went in and out of 4 wheel drive and low range. Next day start it up and it’s broken again. So I changed the motor on the transfer case thinking maybe it don’t know what range is in or something Put the fuses in and all was good till the next time I started it.
At this point I’ve come to the conclusion there is something else wrong. So I plug my scan tool in again and I still can’t communicate with the transfer case. Unplug the fuses and plug it all back together the works as it should and now I can communicate with with the transfer case. It had 1 code U1000.
So now I’m thinking it’s actually a problem with the TCCM. Are these vin programmed or am I able to just pull one out of a junk yard and see if it works?
it’s odd it will work just like it should till I let it sit for a few hours or over night then it breaks again.
So I replaced the switch 1st put the fuses in and it seemed that all was fixed. Truck went in and out of 4 wheel drive and low range. Next day start it up and it’s broken again. So I changed the motor on the transfer case thinking maybe it don’t know what range is in or something Put the fuses in and all was good till the next time I started it.
At this point I’ve come to the conclusion there is something else wrong. So I plug my scan tool in again and I still can’t communicate with the transfer case. Unplug the fuses and plug it all back together the works as it should and now I can communicate with with the transfer case. It had 1 code U1000.
So now I’m thinking it’s actually a problem with the TCCM. Are these vin programmed or am I able to just pull one out of a junk yard and see if it works?
it’s odd it will work just like it should till I let it sit for a few hours or over night then it breaks again.
