About Me Forums Automotive 2001 Blazer 4WD Modual Fix

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    Hi Kyle,

    Thanks four the information you posted on blazers 4*4 module. I have a 2001 blazer. My service 4WD light came on a couple nights ago. Took the truck to a fireman’s meeting that night and it shifted form 2 hi to 4 auto several times with no problems. The next morning grabbed the blazer manual did some reading and checked the transfer case oil which was fine. Then checked the front differential and that was low. Filled that with fluid to the proper level Went to check the rear differential and there was no plug. Thought that would fix the problem. Started the truck, 4WD light was still on. Took the truck out for a spin, tryed shifting into 4 hi, made the shift alright. Tried shifting back into 2 hi and it would not make the shift. It would not shift into 4 low either. It would shift into 4 auto and back to 4 hi but that was it. The truck was stuck in 4 hi. Not to good for the truck to drive on dry pavement, especially if you turn sharp. You can really feel it in the steering wheel.

    Went online and found a site that told me to check the vacuum switch under the battery. So I took out the battery and the mounting plate, of course one of the nuts falls in between the double wall out of site. Least of my worries right now. Ran jumper cables from the battery to the battery cables to start the truck and switched into 2 hi. Watched the vacuum switch and it let go twice and then pulled back. So I figured that part was working ok. Grabbed the cable that goes from there to the front differential to try moving it. Could move it but not much. So I went underneath the truck and disconnect the cable from the front differential. Cable was a nice shinny silver and moved back and forth freely. So that eliminated cable freeze up. Was beginning to think that maybe I froze something up in the front differential when it was low on fluid. I never check the fluid since I owned the truck. But it never made any noises when driving in 4 wheel or 2 wheel.

    So back on line and I found your site. The next morning I checked the obvious 4WD fuse inside the truck, that was fine. Then I pulled every fuse inside the truck and under the hood with no avail. Removed the right front kick panel, pulled the 4WD module. Removed the 32 pin plug and saw a bunch of green stuff at the bottom of the plug. Removed the 4 pin plug and that had white stuff on the pins. Began to clean the pins on the 32 pin plug and notice pin 1 was kind of loose in the module. Crap this is not a good thing. So what have I got to loose. Took off the mounting bracket bent the tabs back on the back, opened the case and saw a green bogger on the back side of the first pin. Scraped it away and about an 1/8″ of pin was gone. Crap again. Ok take a piece of wire solder it to the little stub then hot glue it so it stays in better. Then drill a hole in the top of the module case to bring the wire threw. Hot glue the wire in the center of the hole so it does not short out on the metal case. Spiced the wire to the wire on the female side of the plug to bypass the the corroded pin. Cleaned about 7 other pins that were also corroded, and added some dielectric. Plugged it back in, started the truck, and well like you said, Houston we have ignition. The Service 4WD light went out and I could shift the transfer case to all 5 positions (2hi, 4auto, 4hi, 4low, neutral for towing). Oh what a feeling. The clicking noise that I use to think nothing of was back and it was like music to my ears. Thanks so much for your info. You saved me a bundle I’m sure. It took me about a day from start to finish. I have some pictures of my fix.


    • This topic was modified 10 years, 2 months ago by Avatar Kyle. Reason: Image formatting
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