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Discussion Starter · #1 ·
I'm sorry if this has been covered (probably many times), but I've looked through the posts and haven't found the answer that makes sense to me. My wife has a 2012 GMC Terrain that has recently started having a hard shift when backing out of the driveway. We recently noticed that the R or D flashes when it's in gear and when this happens, the car hesitates to accelerate. It's pretty much a crawl until it gets to 20 mph and then its ok, which is hard to deal with when getting on the interstate. We took it into the local dealer (we just moved here so it was the only option) and they replaced the solenoids. It was fixed for a week and then the problem happened again. It's not so concerning except when it happens on the interstate. So I'm guessing it's the TCM and it was a recommended GM suggestion on their report when they replaced the solenoids.

So my questions. Can I fix this myself or does this require programming and timing? I'm fairly competent around engines, but electronics obviously may require tools that I don't have/. Is this common or is there something else I should look out for?

Thanks in advance
 

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Read this whole thread for clues and pics on removing the tcm.
Similar trans so should be the same.
I think 2012s dont use the laminate discs, but youll get a better idea.

 
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2021 Terrain SLT Elevation
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Read this whole thread for clues and pics on removing the tcm.
Similar trans so should be the same.
I think 2012s dont use the laminate discs, but youll get a better idea.

Read this whole thread for clues and pics on removing the tcm.
Similar trans so should be the same.
I think 2012s dont use the laminate discs, but youll get a better idea.

Excellent write-up! I couldn’t find any info that relates to our 2017 Buick Encore (27k)that just experienced a hard shift, through codes but continued to drive fine. Dealership said they would run diagnostics on it for $150 and estimated cost to be $3300.00 thats not going to happen. What a joke GM this should be covered since it is internal to the transmission
 

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'16 Equinox LTZ AWD 3.6
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3/36 warranty is what it is no matter the brand. Time or miles whatever comes first.
My D in L '16 3.6 'nox just had to have the trans. replaced. Extended warranty covered it. Only 70k miles on it and fluids were serviced by me at 40k when she bought it at 40k. 40k fluid did not look super dark either.
Symptoms were hard downshifts when stopping when trans was fully warmed up.
Procedure was first to inspect valve body for debris and recalibrate. the TCM per warranty Co. After that was done it was no Bueno. Reman. trans went in.
 
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