Compatibility of different TCCMs for 4x4 Envoys, Trailblazers, etc.

[Ironring1]

Hi, all. I have a used 2002 Envoy SLE (4.2 I6) that is in great shape, except for no transfer case control (surprise surprise...)

At any rate, I get the classic "lights on control switch light for a few seconds at start up, then turn off, with check 4WD light on dashboard". So, the switch most likely is good, and I've tried the fuse-pull approach to waking up the TCCM with no luck. I'm about to order a TCCM off of eBay, but before I do, I want to confirm the inter-compatibility of the different modules.

Which TCCMs can swap for each other? So far, I have run across several different GM TCCM model numbers, and I read somewhere that there may be as many as 12 different ones. Will any of these work in my 2002 Envoy? Are there particular model numbers to avoid (e.g., the ones that were in the 2002 vehicles?). I can see that there are bits and pieces of information that one can piece together from different posts, but I thought that it would be a good idea to have a single, clearly labeled forum thread about the compatibility of different models of TCCM to put that issue to rest.

Thanks,
-Chris

 

[The_Roadie]

Welcome! I've posted about the part number issue many times, as recently as this week as a matter of fact. There should be an sticky thread, but alas, nobody's had time. Just search to find the part numbers.

You're right - ANY 2002 TCCM is suspect. That's why GM redesigned it and places like parts4chevys.com list the new part numbers only. If you search there or Rockauto for a part number that's been superceded, it will tell you.

That said, even if you get a new part number TCCM that's been used, it will have been programmed for the vehicle. 4WD systems with a LO range include the TB, Envoy, and Bravada. AWD TCCMs you want to avoid were used in the Saab 97X and the Rainier. I forget what system the Isuzu used but you will almost never find one of them in the junkyard.

 

[Ironring1]

That said, even if you get a new part number TCCM that's been used, it will have been programmed for the vehicle. 4WD systems with a LO range include the TB, Envoy, and Bravada. AWD TCCMs you want to avoid were used in the Saab 97X and the Rainier. I forget what system the Isuzu used but you will almost never find one of them in the junkyard.

Ah! This is important new information to me! So regardless of the source of the replacement TCCM, I will have to get it programmed. Is this something that most well-equipped garages can take care of, or is this something that will need to go to the GM dealership to get done? Also, how much should I expect to pay for this (I realize that prices vary from place to place, but an approximate cost estimate would be good enough) Finally, is this something that I need to have done to the TCCM before I install it in my Envoy, or can I install it in the vehicle, then drive over to the dealer and have them program it in place?

Thanks again,
-Chris

 

[The_Roadie]

Sorry if I wasn't clear.

NEW units, virgin off the shelf from a GM authorized source, need to be programmed while in the vehicle. Only GM dealers can do this, and they charge up to $100 for a ten minute job, it's been reported.

NEW Dorman aftermarket units just came onto the market, and they cost a little less, and do NOT have to be molested by a dealer, so the price you pay is the price you get.

USED junkyard or Ebay units if they come from a 4WD TB, Envoy or Bravada, are plug and play. Work without the dealers touch.

USED units from the "wrong" sort of AWD vehicle can be made to work in a 4WD vehicle, but only by visiting the dealer for a reprogramming.

Hope this was a definitive list.

 

[freddyboy61]

As Roadie said, if you get a used TCCM from a TB, Envoy or Bravada, you will not have to have it programmed. But if you buy a brand new one, it will require programming, and the dealer will probably charge you for a one hour rate ($80 - $100)

 

[Ironring1]

Excellent. Thank you both for your help. I have a used TCCM from a 2005 Trailblazer on its way. I will post back to update my progress. I don't know when the TC fluid was last changed (used vehicle, new to me), so I will change that while I am at it reset that clock, too. From what the previous owners told me, everything had been serviced regularly, but since they didn't drive outside of the city, they didn't want to pay the $100~$200 to reprogram the TCCM and left the vehicle in 2HI. I'll let you know how I fare

 

[yar02169]

Roadie-

You are a valuable source of information on this site, but I think you made a slight error. The Bravada has the Smart Track AWD system. No buttons on the dash, it's all automatic, it does not have a Lo Selector Switch.
The Bravada should be grouped in with the 97X, and Rainer.
For some reason I think I read somewhere that the Envoy could go either way, depending on options, but I could be wrong on that.

 

[The_Roadie]

I think you made a slight error. The Bravada has the Smart Track AWD system. No buttons on the dash, it's all automatic, it does not have a Lo Selector Switch.
The Bravada should be grouped in with the 97X, and Rainer.

Arghhhhh. I *do* have a leaky memory on that. THANKS!!! It's the Isuzu Ascender that shares the NP226 transfer case (with LO range and a switch) with the TB and Envoy. I promise to remember it now.

I used to get cranky when I was young(er) back at Trailvoy and goofed up and got corrected. I photoshopped this comic to slap down. Now I embrace corrections because I have lost a few million more brain cells (bet nobody new can possibly guess my age.)

 

[The_Roadie]

Oh, and I can guarantee the Envoy never had the NP126 TC as an option. The platform came 4WD or AWD (or 2WD) but there wasn't that much optionability.

 

[Darkrider_LS]

Sorry if I wasn't clear.

NEW units, virgin off the shelf from a GM authorized source, need to be programmed while in the vehicle. Only GM dealers can do this, and they charge up to $100 for a ten minute job, it's been reported.

NEW Dorman aftermarket units just came onto the market, and they cost a little less, and do NOT have to be molested by a dealer, so the price you pay is the price you get.

USED junkyard or Ebay units if they come from a 4WD TB, Envoy or Bravada, are plug and play. Work without the dealers touch.

USED units from the "wrong" sort of AWD vehicle can be made to work in a 4WD vehicle, but only by visiting the dealer for a reprogramming.

Hope this was a definitive list.

This is a good bit of info! I would have ran into this the hard way and wondered wtf just happened! So the Dorman TCCM you can get from rockauto doesnt need the reprogramming...hmmm good to know!

 

[djthumper]

Exactly, they are plug and play.

 

[Darkrider_LS]

Exactly, they are plug and play.

Awesome! Def gonna order one now to have on hand even if it ends up i dont need it at this point. Better to have it and not need it then to need it and not have it.