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So, how did you know the TC gear had exploded? It threw a CEL or a 4x4 dash light, I presume? Anywho, it must've been a major pain in the *** to get that fixed... unless you have a friendly scrap yard not too far away with reasonably priced spare TCs. I don't and the local junkyard charges almost like a freakin dealership! (and they won't even pay you a dime for your old car or truck if you bring it in...)
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Service 4x4 light was on, but my code reader was no help. Whenever I would start the truck, the box would emit a few clicks. Selecting 4wd Hi and Lo would blink a few seconds, then return to 2wd. Anyway, my battery kept dying.
So one day I unplugged the control unit down by the passenger kick panel. Battery didn't drain anymore. Hooked back up, battery would drain and die in about 8 hours (new battery BTW).
I got a used computer off e-bay, and the same thing happens. Dead battery. I did notice that the TCM would churn for about 10 seconds every time I reconnected the battery. So, I ordered a Dorman () motor off e-bay.Think I paid about $150.00 US.( Lifetime warranty is the only reason I buy Dorman parts). When I removed the old TC motor, I noticed it has a white paint dot on it, indicating salvage yard.
When I bought the truck, 4WD wasn't working. Seller told me he put a new vacuum switch in (fire wall). Looks like he also replaced the TCM.
Hopefully I won't get to find out about how to perform any more repairs anytime soon, lol! I've had enough of those lately... and they all seem electronic or electrical-related in one way or another, which makes me fear the future a little bit with this particular vehicle (considering how much electronic junk is on cars/trucks these days that could theoretically break down).
There is nothing common between the 3-button & 4-button switches aside from the connector. The 3-button switch has 3 discretely switched circuits inside while the 4-button switch has 1 circuit & chances the resistances seen on that circuit which the TCCM senses thereby commanding the encoder motor on the transfer case to change modes/ranges. They cannot be swapped. Different systems entirely so use the proper parts.
There is nothing common between the 3-button & 4-button switches aside from the connector. The 3-button switch has 3 discretely switched circuits inside while the 4-button switch has 1 circuit & chances the resistances seen on that circuit which the TCCM senses thereby commanding the encoder motor on the transfer case to change modes/ranges. They cannot be swapped. Different systems entirely so use the proper parts.
Allright, that's a pretty complete and a very reasonable answer. In essence, it's 100% no go between the two. Thanks for the input!
Another question though: now, with my old 4 button switch re-soldered and fixed, the round "Auto 4WD" button is lit all the time when the ignition is on. I can still switch between 2WD and 4x4 modes, but the auto 4WD mode is always on (yellow LED). I was wondering if that's normal?
Anyway, I fixed my old 4 button dash switch and it works again. I took it apart and looked at the reverse side of the plug connectors inside the switch (at the solder points). Well, the 4 pin plug area looked like one of the solder points had a microscopic crack, almost invisible to the naked eye. The 8 pin plug area looked fine at a glance, but who knows what was really going with that as well. We have cold winters here (Canada) and cheap solder sometimes has a tendency to fail in very low temperatures.
So, out comes my trusty 40W soldering iron and some solder. Once the iron was in operating temp, I heated each pin from the top first for 5-6 seconds, then melted the solder around it for 3-4 seconds in order to have it "sink in" a little bit into the pin hole on the board. I added some solder to pins which seemed to have less solder than others and did all 12 pins this way. Note: caution needs to be taken not to touch the solder from one pin to another... otherwise the board could short out!
Upon completion, the switch was reassembled, plugged in and... hooray! Now it works in all positions without any pressure being applied to the back of the blue plug. It's funny how solder points could fail like that though... as they used to work fine for many years (since 2001 till about last year). It is important to note that the switch was used very rarely (as the 4x4 is rarely needed since roads are always plowed in winter out here) and was never taken out of the dash previously. The solder points just failed by themselves with time.
This, coupled with the recently failed (and repaired) ABS control module and a defective fuel pump sensor are just a few of the ****-offs I seem to be having with this truck. Funny how my '99 Ford Explorer (roughly same mileage, but 2 years older) never has any electronics problems at all and runs like new day after day since I've owned it (2002). Maybe it's time for GM to pay a bit more attention to quality control with their electronics (and yes, I've had experience with other GMs such as Chevy Ventures, Pontiac Montanas and Outlanders too... all of them having had some funky electronics issues and "mystery lights" on the instrument cluster randomly coming on). That said, I still like my Jimmy for what it is: a body-on-frame RWD true and blue SUV, not some soccer mom FWD frameless abomination à la Equinox/Terrain that only looks like a truck... except that I don't have as much faith in the Jimmy as I do in my '99 Ford due to crappy Chinese quality electronics. In all fairness though, the powertrain is problem-free and runs like a champ on the Jimmy, same as the Ford.
That said, the mind-bending question still stands : How would one go about making a 3 button switch fit on a 4 button Blazer/Jimmy and/or vice-versa? I have a feeling that the answer to this question will more than likely help quite a few other Jimmy/Blazer/Bravada owners who experience switch problems. Thanks!
P.S. I now have a 100% working, bright yellow LED 3 button 4x4 switch for sale (for a 98-05 Blazer/Jimmy/S-10/Bravada with 3 buttons). Comes with plugs too and about 1" of wires.
How about $20 shipped to Canada/USA? (my cost) Paypal only. Please PM if interested.
I have the 4 button switch for my 1999 Blazer - I want tp buy a replacement TCCM - they all seem to be PN 15741322-would this be correct for the 4 buttonsystem 4WD?. Thanks
) motor off e-bay.Think I paid about $150.00 US.( Lifetime warranty is the only reason I buy Dorman parts). When I removed the old TC motor, I noticed it has a white paint dot on it, indicating salvage yard. 
