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So, you thought your transmission woes were over. GM rebuilt your transmission after the infamous wave plate failure and you figured you were good for another 100K. Wrong, suddenly you have the familiar check engine light and transmission won't shift past 2nd gear. Ahhhhh. You'll have another P0700 code along with some sort of shift solenoid failure. In my case it was a P0752, but there’s several switches on the module that could fail and trigger similar codes.
This is another flaw in the GM transmission that may have been exacerbated by the wave plate failure. The Transmission Electro-Hydraulic Control Module, often called TEHCM or TCM, is another non-robust part in the terrible transmission on these things. The TEHCM is a multi-purpose part that acts as the transmission control computer along with some sensors and shift solenoids. It lives inside the transmission and swims in the transmission fluid. So, the metal particles flowing through your transmission during the wave plate failure, or any overheat conditions, will weaken the TEHCM also.
GM doesn't always help on these, so you're probably on your own to pay for the repair. My dealer wanted $1400 for the repair. Coincidentally that's the same amount I had to pay out-of-pocket for the wave plate failure rebuild. Even with GM's help, this is an expensive transmission to get 120K miles out of.

Let’s jump right to the issue:



The shift solenoids (or switches depending on the document you’re reading at the time) just kind of fall apart. To replace these simple and inexpensive parts, you also have to replace the more expensive parts contained in the rest of the module. GM charges $650 for a TEHCM and the dealer will want $1400 or so for the entire repair. The repair involves replacing the module, some gaskets, and reprogramming the TEHCM. Earlier this year (2015), Dorman came out with a plug-and-play kit to do the repair yourself. The retail price of the Dorman pre-programmed TEHCM is around $300. You’ll also need about $50 worth of transmission fluid and optionally some gaskets. I leave the gasket question up to you. I didn’t replace them, but I will talk about them during the discussion.

Can you do it?
This is a fairly simple procedure. If you have managed to replace a headlight bulb in this thing you’re definitely good to go. I’d say it is on par with a brake job in complexity. If you can’t change the air filter, pay the dealer.
Alldata says it's a 3.1 hr procedure (2.2 if under warranty). It took me around 4 hrs. with a couple breaks.
If you attempt this, be prepared. You, the ground, and your tools to be soaked in transmission fluid. It never stops coming.

Next 2 Posts:
- What you need
- Basic Procedure
 

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Discussion Starter #2
What you need
1. Dorman TEHCM (part 609-000) – I bought it at Summit Racing for $289 including shipping. They also take a $300 core charge which is returned when you send back your old TEHCM. Whoever you order the part from will need your VIN to ensure it is programmed properly for your vehicle. If they don't ask for it, make sure you tell them they will need it.



2. 5 quarts of Dextron VI Automatic Transmission Fluid – Not cheap at somewhere around $8/quart if you buy it at a local auto parts box.
3. Optionally gaskets for the transmission cover and TEHCM connector. I didn’t replace these and didn’t research how much they even cost. The GM procedures highly recommend replacing these.
4. Subscription to alldatadiy.com – This is $26 well spent for this repair. I will not reproduce their materials here, so it is absolutely necessary to get the bolt locations and torque order for the TEHCM bolts. They are a multitude of different lengths and have a very specific torque order to assure module alignment.
5. Selection of sockets and wrenches. You need 11mm for the transmission drain plug, and I believe every thing else is 10mm. A ¼ drive with 8mm and 10mm regular and deep sockets should do the job. If you are unsure what 109 in/lb means, you may want a torque wrench in that range. But, if you use a short ¼ drive and don’t crank down too hard, you should be pretty close. You’ll also need some short extensions to reach some areas and I’d suggest getting one of the small round ratchets with no handle (the blue thing in the box).
6. Racheting wrench. The biggest issue with this repair is fitting tools into tight places. You’ll want one of these.
7. Torx T25 – If you’ve done an air filter change you know what you need. If you know the engineer that designed that airbox, kick him in the nuts repeatedly for me. But, essentially you need a T25 socket. Just a regular T25 screwdriver won’t do it.
8. Screwdrivers
9. I suggest a helper for 10 minutes to help hold the TEHCM in place during installation. Otherwise it will be all too easy to drop it.

 

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Discussion Starter #3
Look in your engine compartment and find the transmission fill dipstick. The plastic cover it resides in covers the TEHCM. The big electrical connector on it connects directly to the TEHCM. You are basically removing that cover, removing the TEHCM, replacing the TEHCM and the cover. But there is a little more to it.

1. Prepare the car. I did mine in my driveway on ramps. My driveway is at a slight angle so the car winds up level with one end up on my ramps. If you have a flat area, put the car on jack stands or jack it up and put cinder blocks under the wheels. You will need to get to the engine compartment and underneath. I used a small step ladder to get good access in the engine compartment while up on ramps.
2. Remove the electrical connector. It’s a little tricky, so make sure you can do this before you get too far. Basically, squeeze the little red lock through the lever then stick a screwdriver in where that lock was and carefully pop the lever out of its detent. Pulling the lever will then remove the connector. Note: when you reinstall make sure the lever is back to start and it will also tighten the connector onto the TEHCM.
3. Drain the transmission fluid. Remove the 11mm drain bolt that is about 2” from the plastic cover on the bottom of the transmission. Just like draining the oil.
4. Remove the airbox. The transmission cover won’t come out with it in place. I removed the top, took the bolt out of the bottom and left it in. But, it constantly gets in the way. If I did it again, I’d take the main engine compartment cover out and remove the entire airbox. The airbox is held into the car with one 10mm bolt and a stud.
5. Remove the plastic transmission cover. There are a bunch of 10mm bolts around it. Alldata will tell you you have to remove one of the transmission lines, but I didn’t have to. Just remove the bolts and the nut that holds the transmission line bracket to one of the bolts. With a little effort you can get it out the top.

Cover Removed



6. Consult Alldata and remove the bolts from the TEHCM in the proper order. You’ll need 8mm and 10mm here. Alldata mentions another module, it comes out with the TEHCM. The Dorman replacement has this module attached, so no need to do anything here.
7. Put the connector gasket on the new TEHCM. I didn’t have the parts and it was Sunday, so I just pulled the gasket off the old one and reused it. It worked fine. I would rather have put a new one on, but didn’t want to wait another week for a weekend day to finish the job. If you look carefully at the pic above you can see the connector gasket around the connector on the TEHCM.
8. Install the Dorman TEHCM. I suggest a helper here until you get a bolt or two in. I almost dropped it twice before getting a helper. Everything is basically blind and you want to make sure you have everything aligned and aren’t scratching the plate up trying to get bolts in. Be very careful with which length bolts go where. You are bolting into the valve body which is pretty fragile. If a bolt resists, double and triple check that you have the right bolt in that hole before putting some umph behind it. Get all the bolts finger tight, then torque them in the order in Alldata. The 4 8mm bolts are first and will align the module.
9. If you have a new cover gasket, install it in the cover. Again, I didn’t replace it and it currently isn’t leaking.
10. Reinstall the cover. Finger tighten all the bolts, then torque them down.
11. Fill the transmission. The specs say a little over 5 quarts, but be careful not to overfill. Mine took just under 5-quarts. It initially took only 4, but after a short drive it was about a quart low.
12. Reconnect the transmission connector.
13. Replace the airbox.
14. Test drive. When you test drive the car, it will shift terribly at first. There is an adaptive shift algorithm in the computer and it will take quite a few shifts before it starts shifting properly. Drive stop and go and get it to shift through the gears up and down as much as possible.
15. Pat self on back. You just saved yourself $1000.
 

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One of the best how-to descriptions in the history of this forum. Well done! :thumb: (still laughing about the T25 comment)
 

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Very good job! This should be posted on the Enclave, Outlook, and Traverse boards also. I check all three other boards along with this one, and am surprised by the number of owner's who only check or belong to one board. A lot of information is missed I am sure when an owner only follows their own vehicle's forum.
 

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Discussion Starter #7
ls973800 said:
Very good job! This should be posted on the Enclave, Outlook, and Traverse boards also. I check all three other boards along with this one, and am surprised by the number of owner's who only check or belong to one board. A lot of information is missed I am sure when an owner only follows their own vehicle's forum.
I sometimes search those forums when I'm looking for something. So far I only post here. Would be much more convenient if it was one board.
 

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stpete,

Thanks for sharing.

I did the waved plates as a preemptive repair. This job help up perfectly.

This repair looks a little easier. I suspect there is no need to change the TEHCM preemptively?

What was the operational symptoms that lead you to he TEHCM repair?
 

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Carbon Black said:
stpete,

Thanks for sharing.

I did the waved plates as a preemptive repair. This job help up perfectly.

This repair looks a little easier. I suspect there is no need to change the TEHCM preemptively?

What was the operational symptoms that lead you to he TEHCM repair?
The symptom is CEL and won't shift past 2nd gear. Reverse still works.

The TEHCM failure tends to start off intermittent. Ours would do it, but a reset of the code would allow the car to drive normally again. I think shutoff for more than some amount of time is equivalent to code reset. So, you can wait for it to fail and still drive the car (with considerable aggravation when it happens).
 

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Two questions, 1) do you have AWD and 2) do you think this is necessary if I'm just getting the code and no other symptoms? Thanks
 

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bluefish7 said:
1) do you have AWD
AWD or FWD shouldn't matter. That portion of the transmission is identical in both setups. As such, the procedure to change it would be the same.
 

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bluefish7 said:
2) do you think this is necessary if I'm just getting the code and no other symptoms? Thanks
If you are getting the code, it's likely just a matter of time. When mine started, it was a pretty rare occurrence that the tranny wouldn't shift beyond 1st gear. After about 4 months it was happening a couple of times a week, and the wife wanted it fixed - TEHCM replacement.
 

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bluefish7 said:
Great info, I guess this will be the winter project for this .
Look at this Sonnax site. There are kits for replacement of the TECHM pressure switch laminate discs (membranes). If that is all that's wrong with the TEHCM, this could save mechanically-savvy folks a BUNCH of money as well as alleviate many technical headaches with programming and such.

http://www.sonnax.com/parts/3758-pressure-switch-installation-tool-kit
 

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Thanks, I'm not sure I have mechanical capability to troubleshoot the TEHCM to that extent, how would you know if the seals are the issue?
 

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bluefish7 said:
Thanks, I'm not sure I have mechanical capability to troubleshoot the TEHCM to that extent, how would you know if the seals are the issue?
Look at the first pic in stpete's post. Trouble with the laminate discs (membranes) is real evident.
 

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That pressure switch rebuild kit is around $150 I believe, at least from the one supplier in GA. I changed out the fluid last week and today the second instance of CEL happened, I guess I should order!

edit: Seems the price of $150 was for a kit with 40 pieces. Also Rock Auto has the TEHCM for about $230 with the same core charge
 

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Thank you OP for the detailed post. This may help me in the near future.

GeoHawk said:
If you are getting the code, it's likely just a matter of time. When mine started, it was a pretty rare occurrence that the tranny wouldn't shift beyond 1st gear. After about 4 months it was happening a couple of times a week, and the wife wanted it fixed - TEHCM replacement.
I am having similar issues on our 2008 FWD (stuck in 1st gear with reverse). Was your waveplate already replaced by the time this happened? I am still in the original Transmission but my guess is the waveplate is going. I first had a code for the TECHM replacement. Then went on vacation for a month. When I came back CEL was gone and car drove fine for a month. Now yesterday I get a CEL again but this time is for the Solenoid (code P0752).

I am wondering if my waveplate is failing and then causing these different codes/problems. If that is the case I recall GM extending the warranty for the wavepalate but not sure how to tell it it's really the waveplate or if it's really a solenoid or TECHM without opening her up. Any clues/tips?

stpete said:
The symptom is CEL and won't shift past 2nd gear. Reverse still works.

The TEHCM failure tends to start off intermittent. Ours would do it, but a reset of the code would allow the car to drive normally again. I think shutoff for more than some amount of time is equivalent to code reset. So, you can wait for it to fail and still drive the car (with considerable aggravation when it happens).
Yeah, that is what I experienced, Although I have a code reader, after about 1 month of inactivity the code reset/cleared by itself.
 

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So is there another gasket around the connector? OP mentions that but I have looked around but have not found the part number. I want to order the gaskets too and prefer to order all at once. I have not seen the OP active in a while so If anyone knows please post the number. TIA
 
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