1999 Jimmy 4WD control problems

Hi to everyone, I am new here. I really need some advice. I have a 1999 GMC Jimmy SLT4.3 V6 4x4 SUV. I am having problems with the 4WD. I also have "Service4WD" light on in the dash. My 4WD control buttons do NOT light up at all, I have replaced the switch with a new one, that didn't help. I have checked all the fuses also. A mechanic scanned it with a scanner and got Code: PO315. "The mechanic said the code= Motor ground circuit open, performed Diagnostic trouble code check, TEAT came to step recommending replacing the Transmission Control Module." I am sorry this doesn't sound logical to me. I feel there must be allot more to check before replacing a very expensive Item, etc like corroded connections, poor ground possible vacuum leaks if this does apply? I am told I have aNP8 transfer case.
I have been Also told there is no way to scan 4WD, this person said it is not part of the data base. He said the only way is to count the code flashes. My problem is the lights don't light.

Any suggestions will be greatly appreciated.
Thanks,
Photohawk

Hey Photohawk,

I was wondering if you ever got a response on this. I have a similar problem.

I have a '99 GMC Jimmy 4x4. My 4WD was not working. The light would flash but not engage. I took it to a transmission shop who changed the motor in the transfer case. The problem now is the 4WD lights on the dash do not light at all and the Service 4WD light now appears. The transmission shop said there is power to to the motor, but they can't figure out how to get the 4WD lights to work - or to engage. They suggested going to a dealer who might have a "tech 2 diagnostic scanner" which could figure out the problem, but I am reluctant to go to a dealer and get raked over the $$$$ coals. Has anyone seen this - if so, suggestions on how to fix it?? Thanks!!

Just to let you guys both know, "YOU WILL NEVER GET AN ANSWER" I posted about mine suddenly going crazy one day and switching on its own, and never got an answer, ended up unplugging it until i get the money to take it in for a look/repair... mine is a 2000 GMC Jimmy. I honestly have thought of just buying each part and switching them out one at a time, at least I could learn what it is and help in the future, but it will be a few months before i have some more expendable cash.

Hi, I am new here, and was very surprized ther wasn't any response other that you. I feel like you I don't want to go to a Dealer and be taken over the coals either. All I know I have driven GM vehicles for over 44 year now, but am totlally dissappointed in GM. I beleive in buying American, but I am sorry it is time to move to a better, dependable vehicle and manufacture.
I have had mine scanned by a local garage, and I believe they don't relly know what is wrong. My brother has GM tech repair manual, he said this darn 4WD system is almost as bad as the space shuttle. I had 93 jimmy neve had any major problems with it, but this 1999 is somehting elese. I feel they made Lemons from 1999 -2001. Gm also has had notorious intake manfold leak problems; which I feel they should have recalled. The 99 is also terrible on gas mileage. Here is also another good group, if management will allow the post.
Thanks,
Phtohawk

http://groups.msn.com/AutoTechsOnline

I have the same friggin problem on a 99. God what a pain in the butt.

Has anyone EVER received any response to this post. I have a 1999 Blazer and was having the same issues, only now I have lost all electrical power. Whenever I try to crank the negine all power goes out. I think a circuit breaker is kicking out somewhere, because I have to disconnect the battery and wait a while. But once I hook it back up and the PCM resets and I try to crank the engine, no power again. Everything goes out, interior lights, underhood lamp, everything.

Has anyone EVER received any response to this post. I have a 1999 Blazer and was having the same issues, only now I have lost all electrical power. Whenever I try to crank the negine all power goes out. I think a circuit breaker is kicking out somewhere, because I have to disconnect the battery and wait a while. But once I hook it back up and the PCM resets and I try to crank the engine, no power again. Everything goes out, interior lights, underhood lamp, everything.

Welcome to AF swpatech.
When a tread is old or almost 2 years old like this one it is best to let a sleeping dog sleep.
Always check the date on a post before posting back to it.

On your problem if you need help click the New Thread button and start your own new post on it.
Give all of the info you can like mileage and what transfer case it has and what it is doing or not doing.
MT