2021 Avenir - Transmission Issue / Info

Gregger

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Buick Envision Avenir
This is more of an FYI to any of the new Envision owners.

Recently the temps dropped to -28C a few days ago. When this happened I remote started my car with no issues. When I got into the vehicle and went through the brake/push start button sequence, a "Service Transmission" message popped up on the digital display and the check engine light came on. After checking everything I pulled out of the driveway and travelled about 100 yards up the street with no issues. I then pulled over and shut the car off without depressing the Park button. The vehicle shut off but didn't go into Park automatically. It started to role backwards. I depressed the brake, placed it in Park, then started it again (it wouldn't start until I depressed the Park button). I drove to the dealership which immediately scanned for a fault code. They asked me to leave the car with them since they found a tranny related code. The service manager asked for my specific symptoms. He did some checking and then asked me if I usually placed the vehicle in Park before shutting the engine down. I said about 50% of the time since the owners manual states the vehicle will go into park automatically when the engine is shut off. He informed me that GM had just put out a bulletin stating that the vehicle should be placed in Park before shutting down the engine to prevent this "Service Transmission" notice from happening. He brought the car into the service bay, had the tranny checked from top to bottom, cleared the codes and informed me to ignore the manual and physically Park the unit before shutting it off. It's been almost a week since it happened and no issues so far.

Anybody else come across this issue? Again, it was quite cold outside and at first I thought it was a valve or solenoid hanging up due to the cold weather and the vehicle being so new.
 

alphabets

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2014 Buick LaCrosse
I have not come across this specific issue, luckily. However, I can attest to the Park function. Without the shifter and while still getting use to the button shifters, sometimes I find myself accidentally hitting the stop engine button before putting the suv in park. Every time I did this the envision did in fact shift the car into park by itself, like the manual states. I have never received an error code but will keep an eye out for that in the future.
 

Gregger

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Buick Ownership
Buick Envision Avenir
Well it looks like this issue or one similar to it has come back to bite me. We drove to Florida and about 1 mile from our location at an intersection the vehicle stopped moving. I had suspected an issue a couple of intersections before when the vehicle started to drop into park as I was coming to a stop for a red light. You could hear the park mechanism ratchet then stop the vehicle with a jerk. When it quit moving the door locks cycled off and on. Park brake seemed to apply. The info center told me to service transmission and when I tried to shift into drive it stated I wasn't meeting the shift parameters (or something like that). I was able to move the vehicle when I shut it off and on getting me to the next light where it quit moving again (to the annoyance of other drivers). This happened several times until I got it to our location. Roadside assistance towed the vehicle to a dealership where after several days they informed me that the problem was electrical and replaced the transmission shift control module. The only issue now is that they can't program the new module to work. GM engineering is now working on the programming issue. I've lost my confidence in this vehicle and in electronic shift mechanisms. This is the first electronic shift I've owned. I purposely refrained from purchasing one for this very reason but I decided to have a little faith... They've had the car for 10 days now. I can't complain about the service I've received. At least they provided me with wheels for the time being.
 

alphabets

Full Member
160
11
18
Buick Ownership
2014 Buick LaCrosse
Unfortunately, not just an electronic shift issue. Just google or search on these forums for the famous Chevy/Buick "shift to park" debacle. Happened on both my previous Regal and Verano. Neither with electronic shift mechanisms. GM has had shifter issues for years.
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Gregger

New member
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Buick Ownership
Buick Envision Avenir
Well, got the car back a couple of days ago and it appears to be back to normal. The new transmission shift control module seems to have corrected the problem. The dealership had trouble programming the new module. Apparently the program has to be paired to the serial number of the new part. From what I understand some upgrade had taken place and GM provided the dealership with an alternate serial number allowing the programming to be completed. Got the car back complete with a fresh car wash. Excellent service. Now to see if it's 100 % over the next few months.
 
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