The BECM failed on my 2017 last summer. No loaner was available and the part was backordered but the dealer told me the car was drivable, so I took it home while I waited for the part. When the BECM had failed, the car operated like a conventional hybrid (ICE was on the entire time). However, I noticed that the air conditioning didn't work, so I didn't drive it much for fear of overheating the battery. Fortunately, I've got 2 other cars that my kids use. It's disheartening that the supply shortage for these parts has gotten worse, not better.

 

Sorry to hear that but after watching the video about the battery I think you were wise to not drive it without the air conditioning. I had another car I could drive, a 2003 Monte Carlo but it is prone to overheating and the temperature here is hovering around 95 to 100 so it's really not an option.

 

Add me to the other Volt owners with a failing BECM. Mine is 2017 model year that has about 49,000 miles on it. The BECM intermittently went down around three times, but always came back to operation after turning the car off. I took mine to a dealer in Danvers, MA on June 7, and they almost immediately knew the problem was the BECM. A national back order for the part with no delivery date. There were at least three other Volt owners at this dealership, and some had been waiting for six weeks.
I'm expecting the BECM to fail completely any day which, based on other reports, will mean I can drive only on the ICE, or in a worst case complete failure of the car's propulsion system.
This is not just a supply problem due to the pandemic by the way, as there were reports going back to at least 2018 of BECM failure and long wait times for the part. Most, if not all, of the Volts with BECM failures had 35,000 to 50,000 miles on the car. So GM has known this part is prone to failure at specific age/mileage for at least two years before the pandemic, and apparently did little to resolve it. Perhaps the pandemic-induced supply chain exacerbated the problem, but I believe GM is using the supply chain issue as an excuse for their poorly managed parts inventory.
As someone noted in a previous post, early Volt and Bolt owners are typically early adopters who are advocates of the technology and are influencers. So pissing off hundreds (thousands?) of Volt owners with disabled cars is not exactly the wisest strategy for GM. I personally will never buy another GM after this issue, despite the fact that I think the Volt is the best vehicle I have ever owned. GM should have used the Volt as a means to help transition ICE vehicle owners to buy/lease EVs without "range anxiety" fear (which isn't really a thing now that most all BEVs get >200 mile range).
Since the dealership is saying GM doesn't provide any updates on BECM deliveries, all I can do is wait and hope the car continues to operate until I one day get the part replaced.

Sept. 7, 2022 update: After waiting nearly 3 months (since June 7) for a BECM replacement without any estimated date of arrival, and hours on the phone with GM/Chevrolet Customer Care Center who knew absolutely nothing about the back-ordered part or when it would ship, I asked GM to "escalate" the case. Other than approximately weekly calls from a Customer Care Center person, who called to ask ME if the dealer had provided in updates on the BECM (?), that resulted in no helpful news or action by GM.
After my frustration level had maxed out, on the week of August 22 I filed the following complaints:
National Highway Traffic Safety Administration (#11480405),
Massachusetts Attorney General’s Office
Better Business Bureau (case #17749200)
I also mailed letters to three GM/Chevrolet corporate offices in Detroit (Chevrolet Customer Assistance Center, 300 Renaissance Center, and a PO Box)
I emailed a letter of complaint to mary.barra@gm.com and munhara.hamza@gm.com (apparently a chief staff person).
Four days later, on August 26, 2022, I received a call from Herb Chambers Chevrolet dealership that the BECM had arrived! They had no information about how or where the part was shipped from. Just mysteriously landed at the dealership!
The new BECM was installed on August 31, and it seems to be working okay.
So the take-home message as I see it, if you want action by GM to get a replacement BECM, you have to go out of your way to be heard and complain. I have no idea which complaint letter or email broke the logjam- I'm guessing Mary Barra's chief of staff, but what do I know.

 

I own a 2019 Volt Premire with approx. 18,000 miles. A full charge is no longer 53 miles of range but only 46 miles of range fully charged. Went to the next city over as Manitowoc, WI dealer had no qualified technicians to service a Volt. That dealer just told me that GM claims 35 miles of range as fully charged is perfectly ok and not subject to any service or warranty!
These BECM modules have been a problem for years as well as GM attitude. The fully charged range varies almost every day. Recently it jumped to 50 miles of range. I bought Hondas for years and sorry I didn't buy a Honda PHEV! I am going to order a BECM, a battery temp sensor, and a battery coolant level sensor and install these myself upon receipt. I don't believe that the problem is battery degradation. There were times the battery would charge to 63 miles of range
during the previous summer on a hot day. I was a GM employee for six years as a tech rep for locomotives and the only tech out of 52 techs that would stand up and conduct a class on anything that EMD/GM manufactured! The division went bankrupt after having 95% of the USA market. GM management was the problem since nothing has changed. Engineering schools haven't changed either!

 

I saw a post here where someone speculated that the BECM failures are low voltage (on the 12V system) related. They speculated that driving with the headlights on (which causes the APM to bump up the voltage on the 12V system) may be a stopgap solution to ward off the demise of the BECM. No idea if it works, but it might buy you some time...

 

On Friday May 27 I parked my Volt with approximately 24 miles of electric range remaining. Later when I got in to start it up, the guess-o-meter showed a full charge but at the bottom of the meter it showed 1 mile of electric range. Shifting to Drive caused the "shift to park" message to appear. Shifting back to Park made the message go away. The car would not move under either electric or gas power. The check engine light was on. By the way, this Shift to Park issue is not the same as the microswitch Shift to Park issue which my car already had repaired earlier under the B2B warranty.

I have an OBDII reader so I checked for diagnostic codes. There were a number of codes including PE100, U2604, U2604, U2605, U2606, U2617, U2618, U2619, U2620, U2621, U2622, U2623 and U2624 which are all associated with the Battery Energy Controller Module failure as detailed on GM Technical Service Bulletin 18-NA-261. My car is no longer under B2B warranty and has just over 40,000 miles on it. However, the BECM as part of the high voltage battery system is covered under the Voltec 8 year 100,000 mile warranty.

On the following Monday I called GM Roadside Assistance which they say you can call whether it is under warranty or not, and described the problem to them. They agreed that it is a Voltec issue and sent a tow truck to take my car to the nearest dealer. The tow truck used a yoke that slides under the front tires. Only later did I see in the owner's manual that they recommend using a flatbed to tow the Volt to avoid damage due to low ground clearance. Hopefully the tow truck didn't damage any of the lower bodywork. I rode with the tow truck driver to the dealership. There is a tow eye stored in the trunk that screws into a left-hand threaded socket under a small panel on the right front of the bumper that flatbed haulers will use along with a cable and winch to pull the car up onto the flatbed. If your car doesn't have one you should get one.

I told the service writer what I knew of the issue and he agreed that it sounded like a Voltec issue and would be covered under warranty. The bad news is he didn't have a loaner car. He said he would give me one if he had one but he just didn't have any. I asked him how I was going to get home and he had the courtesy driver take me home. He said he would call me as soon as he had a loaner available. He said they sometimes get rental cars from Enterprise but they can only rent Chevys and Enterprise doesn't have any right now.

Later that day he called and said that my car had a "Service Keyless Start System" error and they needed to fix that before they could fix the BECM. That error causes the pushbuttons on the door handles to not work sometimes. It was an intermittent problem that I was not too worried about but he basically forced me to agree to a $300 repair before they could get on the BECM. I agreed to the repair to help expedite things.

Two days later he called to tell me that they completed the Service Keyless Start repair and were still waiting on the part for the BECM repair. I asked about the loaner and he said he expected some to become available soon and he would call me. He didn't.

Fast forward a week and no word about a loaner or the status of the BECM repair. I called to get an update but was told that he was busy and nobody else could help me. I left my callback number. He never called me back. I waited a couple of days for the callback but it never came. Then I called the GM lemon hotline that provides assistance before you report the dealership to the BBB or to a lemon law lawyer so they can have a shot at turning things around before it's too late. They told me that I could expect a call within 24 to 48 hours from a customer service specialist and that the specialist would contact the dealer and find out what was going on. Sure enough a young lady called me the next day (a Saturday). I described the issue to her and she said she would call the dealership on Tuesday. I asked why not Monday, and she said she didn't work on Monday. She called me today Tuesday June 14th and said she called the dealership but they didn't answer so she left a message on their voice mail. She also stated that with reference to the loaner car, GM would reimburse me for a rental car if the dealership was unable to provide one. She said it didn't matter what kind of car I rented, it didn't have to be a Chevy. The only problem with that scenario is that I live alone in the country and am far away from any car rental places or Ubers so getting there is a problem. Also the closest rental place doesn't have any cars to rent at least for the next week.

I called the dealership this afternoon and asked for an update. He said that the part is back-ordered and had no further information about availability. I asked about the loaner and he said he expected one to be returned today or tomorrow and he would call me as soon as it was available, and would send the courtesy driver to come get me. I guess I'll find out if he's blowing smoke again.

Bottom line, the good news is that it's covered by the Voltec warranty. The bad news is being without my Volt for an extended period and not having a loaner car is a major inconvenience.

Also I watched the video about removing the Volt battery and replacing the BECM and I do not have a lot of confidence in the dealer mechanic's ability to carry out this repair successfully. It's really complicated and there are a lot of things that can go wrong if they don't do it correctly. I hope GM provides some kind of guidance or assistance to the dealerships for carrying out these repairs. Why they didn't figure out a way to make that module accessible from the passenger compartment through a removable hatch is beyond me. It's mounted right on top of the battery pack.

Update - Wednesday June 15 the service writer called and said he finally had a loaner car for me. The courtesy driver came to my house and took me to the dealership. They gave me an Equinox with 8000 miles on it as a loaner. I'm not sure if calling the GM lemon line had anything to do with it but at least they finally came through with a loaner. He did tell me that the BECM is still on backorder with no indication of availability. Hopefully it comes in soon.

Update July 14 BECM is still on order, still have a loaner.

Update August 17. BECM still on order with no updates on expected availability, still have the loaner. Coming up on 3 months in the shop. GM customer service lady calls once a week asking me if I have any updates for her. Today she said GM wants to offer me $10,000 for the inconvenience. I said what? She corrected herself and said they want to offer me 10,000 POINTS in GM services for each month my car has been waiting for the part. I asked her what it could be used for and she said it could be redeemed for oil changes and such services or if I have enough I can apply it to the purchase of a car. I asked her what 10,000 points amounts to and she said approximately $100 per month. She said she would email me the offer and I have to sign up to receive it. I asked if she had my email address and she read back a crazy email that was not mine. I gave her the right address but have not received the email. I'm pretty disgusted with this process.

What MONTH/YEAR was your 2018 Volt manufactured? Their is a plaque on the driver door jam that sates the build date. I read that early year 2018 cars are effected but later builds are not. I have a 2018 that was manufactured in July 2018 so I am hoping they fixed the BECM issue by then.

 

Update - September 14th
I don't know the build date because the dealership has my car, I haven't seen it since the beginning of June. I still have the Equinox ICE loaner car, what a piece of crap it is compared to my Volt.

My Volt is still at the dealership awaiting the BECM replacement part. GM has said that the "component" needed to fix it is "in transit". That was a week ago and I have heard nothing further.

The Voltec 8 year 100K warranty clock is still ticking even though I am being deprived of the use of my car. Will they extend the warranty out of fairness? I don't think they will.

At the suggestion of the GM Customer Service rep I set up a GM rewards account so I could received the 10,000 points per month of inconvenience that she offered as I noted previously. I informed the rep that the account was set up a couple of weeks ago but to date there are zero points in the account. I probably wouldn't use them anyway but it points to the general incompetence of GM in handling this situation. I have gotten two form letter emails from GM Customer Service to my email address but they are addressed to someone else and the rest of the form letter has fields that are supposed to be replaced by contact information for the rep but they just say <insert extension number here> for example. What a joke.

Will I ever buy another GM vehicle? It's doubtful.

 

Update - September 14th
I don't know the build date because the dealership has my car, I haven't seen it since the beginning of June. I still have the Equinox ICE loaner car, what a piece of crap it is compared to my Volt.

My Volt is still at the dealership awaiting the BECM replacement part. GM has said that the "component" needed to fix it is "in transit". That was a week ago and I have heard nothing further.

The Voltec 8 year 100K warranty clock is still ticking even though I am being deprived of the use of my car. Will they extend the warranty out of fairness? I don't think they will.

At the suggestion of the GM Customer Service rep I set up a GM rewards account so I could received the 10,000 points per month of inconvenience that she offered as I noted previously. I informed the rep that the account was set up a couple of weeks ago but to date there are zero points in the account. I probably wouldn't use them anyway but it points to the general incompetence of GM in handling this situation. I have gotten two form letter emails from GM Customer Service to my email address but they are addressed to someone else and the rest of the form letter has fields that are supposed to be replaced by contact information for the rep but they just say <insert extension number here> for example. What a joke.

Will I ever buy another GM vehicle? It's doubtful.

 

jimbar99 I have a 2017 Volt that had a BECM failure issue, and after waiting nearly 3 months for a replacement part I was getting nowhere with GM customer service. My Volt was more or less driveable, although to do so required turning the car off and on about a dozen times to get out of the "shift to park" mode. Out of desperation, I decided to to vent my anger by writing complaint letters and emails: U.S. Transportation and Safety Administration, Better Business Bureau, Massachusetts Attorney General Office, GM/Chevy Customer Service Dept. (two separate Detroit addresses). I even emailed GM CEO Mary Barra and her "chief of staff". Five days later, my dealership called to inform me the BECM for my car had been delivered. No one at the dealership could explain how or why the part had suddenly appeared after a 3 months wait, but I want to believe I shook someone's tree somewhere to move the BECM to the dealership.
It's certainly worth the 1 hour I spent tracking down addresses, email addresses, and writing letters to have a functioning Volt again.

 

Five days later, my dealership called to inform me the BECM for my car had been delivered. No one at the dealership could explain how or why the part had suddenly appeared after a 3 months wait, but I want to believe I shook someone's tree somewhere to move the BECM to the dealership.

Based on the posts here, a 3 month wait time seems about the norm.

 

On Friday May 27 I parked my Volt with approximately 24 miles of electric range remaining. Later when I got in to start it up, the guess-o-meter showed a full charge but at the bottom of the meter it showed 1 mile of electric range. Shifting to Drive caused the "shift to park" message to appear. Shifting back to Park made the message go away. The car would not move under either electric or gas power. The check engine light was on. By the way, this Shift to Park issue is not the same as the microswitch Shift to Park issue which my car already had repaired earlier under the B2B warranty. I have an OBDII reader so I checked for diagnostic codes. There were a number of codes including PE100, U2604, U2604, U2605, U2606, U2617, U2618, U2619, U2620, U2621, U2622, U2623 and U2624 which are all associated with the Battery Energy Controller Module failure as detailed on GM Technical Service Bulletin 18-NA-261. My car is no longer under B2B warranty and has just over 40,000 miles on it. However, the BECM as part of the high voltage battery system is covered under the Voltec 8 year 100,000 mile warranty. On the following Monday I called GM Roadside Assistance which they say you can call whether it is under warranty or not, and described the problem to them. They agreed that it is a Voltec issue and sent a tow truck to take my car to the nearest dealer. The tow truck used a yoke that slides under the front tires. Only later did I see in the owner's manual that they recommend using a flatbed to tow the Volt to avoid damage due to low ground clearance. Hopefully the tow truck didn't damage any of the lower bodywork. I rode with the tow truck driver to the dealership. There is a tow eye stored in the trunk that screws into a left-hand threaded socket under a small panel on the right front of the bumper that flatbed haulers will use along with a cable and winch to pull the car up onto the flatbed. If your car doesn't have one you should get one. I told the service writer what I knew of the issue and he agreed that it sounded like a Voltec issue and would be covered under warranty. The bad news is he didn't have a loaner car. He said he would give me one if he had one but he just didn't have any. I asked him how I was going to get home and he had the courtesy driver take me home. He said he would call me as soon as he had a loaner available. He said they sometimes get rental cars from Enterprise but they can only rent Chevys and Enterprise doesn't have any right now. Later that day he called and said that my car had a "Service Keyless Start System" error and they needed to fix that before they could fix the BECM. That error causes the pushbuttons on the door handles to not work sometimes. It was an intermittent problem that I was not too worried about but he basically forced me to agree to a $300 repair before they could get on the BECM. I agreed to the repair to help expedite things. Two days later he called to tell me that they completed the Service Keyless Start repair and were still waiting on the part for the BECM repair. I asked about the loaner and he said he expected some to become available soon and he would call me. He didn't. Fast forward a week and no word about a loaner or the status of the BECM repair. I called to get an update but was told that he was busy and nobody else could help me. I left my callback number. He never called me back. I waited a couple of days for the callback but it never came. Then I called the GM lemon hotline that provides assistance before you report the dealership to the BBB or to a lemon law lawyer so they can have a shot at turning things around before it's too late. They told me that I could expect a call within 24 to 48 hours from a customer service specialist and that the specialist would contact the dealer and find out what was going on. Sure enough a young lady called me the next day (a Saturday). I described the issue to her and she said she would call the dealership on Tuesday. I asked why not Monday, and she said she didn't work on Monday. She called me today Tuesday June 14th and said she called the dealership but they didn't answer so she left a message on their voice mail. She also stated that with reference to the loaner car, GM would reimburse me for a rental car if the dealership was unable to provide one. She said it didn't matter what kind of car I rented, it didn't have to be a Chevy. The only problem with that scenario is that I live alone in the country and am far away from any car rental places or Ubers so getting there is a problem. Also the closest rental place doesn't have any cars to rent at least for the next week. I called the dealership this afternoon and asked for an update. He said that the part is back-ordered and had no further information about availability. I asked about the loaner and he said he expected one to be returned today or tomorrow and he would call me as soon as it was available, and would send the courtesy driver to come get me. I guess I'll find out if he's blowing smoke again. Bottom line, the good news is that it's covered by the Voltec warranty. The bad news is being without my Volt for an extended period and not having a loaner car is a major inconvenience. Also I watched the video about removing the Volt battery and replacing the BECM and I do not have a lot of confidence in the dealer mechanic's ability to carry out this repair successfully. It's really complicated and there are a lot of things that can go wrong if they don't do it correctly. I hope GM provides some kind of guidance or assistance to the dealerships for carrying out these repairs. Why they didn't figure out a way to make that module accessible from the passenger compartment through a removable hatch is beyond me. It's mounted right on top of the battery pack. Update - Wednesday June 15 the service writer called and said he finally had a loaner car for me. The courtesy driver came to my house and took me to the dealership. They gave me an Equinox with 8000 miles on it as a loaner. I'm not sure if calling the GM lemon line had anything to do with it but at least they finally came through with a loaner. He did tell me that the BECM is still on backorder with no indication of availability. Hopefully it comes in soon. Update July 14 BECM is still on order, still have a loaner. Update August 17. BECM still on order with no updates on expected availability, still have the loaner. Coming up on 3 months in the shop. GM customer service lady calls once a week asking me if I have any updates for her. Today she said GM wants to offer me $10,000 for the inconvenience. I said what? She corrected herself and said they want to offer me 10,000 POINTS in GM services for each month my car has been waiting for the part. I asked her what it could be used for and she said it could be redeemed for oil changes and such services or if I have enough I can apply it to the purchase of a car. I asked her what 10,000 points amounts to and she said approximately $100 per month. She said she would email me the offer and I have to sign up to receive it. I asked if she had my email address and she read back a crazy email that was not mine. I gave her the right address but have not received the email. I'm pretty disgusted with this process. Update October 17. After over 4 months, the dealer called and said my car is ready for pickup. No advance notice and the dealer has not been communicating with the GM Customer Service lady who calls them weekly for updates. They just don't call her back. When I returned the loaner the service writer laughed and said "I bet you thought you would never see your car again". I didn't find it particularly funny. I had to pay $400 to get my car back because it had the Service Keyless Start System error that they said had to be corrected, costing $200 out of pocket before they would do the warranty repair, and they said the 12V battery needed replacement for another $200. I'm not sure if sitting for 4 months would affect the battery but I said OK and paid the $400. My car was partially charged, and I drove home about 10 miles, parked it and plugged in the charger. When I got in the car the next day, the Service Keyless Start System message appeared on the dash once again, so apparently the $200 I spent to fix it was wasted. I also noticed there was a vibration while driving on the smooth highway. My nephew suggested that maybe the tires had flat spots from sitting still for 4 months on the dealer lot. I don't know about that but I am very unhappy with the situation. The GM Customer Service rep gave me 80,000 points on the GM Rewards program which is apparently good as credit for service at the dealership, which I will never use. She said 10,000 points equates to $100. She called back yesterday for an update on how I was enjoying my car and I told her of the problems. Then she offered me 1 year of free maintenance and 1 year of OnStar for free. She said the maintenance would include things like transmission fluid and cabin air filter. I told her that I didn't want or need OnStar, and I wouldn't be taking my car to the dealer for routine maintenance. She said she would see if there was anything else she could do. Update November 30 - GM Customer Service called last week and said they were processing a GM Goodwill Authorization award that would be good toward the purchase of a new GM vehicle to keep me as a happy GM customer. I asked what that would be worth and she said "half". I was excited for a minute. I asked if I traded in my Volt they would cover half of the difference, she said yes. Today they sent me an email and the Authorization is for a fixed $3500 toward the purchase of a new vehicle. Once again they misinformed me. I told here that amount was insulting given the inconvenience I have been put through plus the fact that they ruined my tires. I told her that I was considering joining the class action suit. She said sorry the amount was less than what I was expecting. 5 minutes later a different GM person called and asked if I had received the certificate. I told her yes but that the amount was completely inadequate. She said she would see if there's anything else they could do and let me know by Monday. I also saw on the My GM Rewards site that the points they gave me could be redeemed against the purchase of a new vehicle and my points are worth $800 so I thought if I can add that to whatever they come up with it might ease the pain a little. The site didn't mention any limits on how many points you could use so I went on chat to make sure I could redeem those on a new purchase. Turns out I can only redeem 25,000 points maximum which equates to $250. What a joke.

Most of us Volt owners have been through this same song and dance with GM promising but not delivering and dealers being incompetent or outright criminal. Our dealer had our 2017 Volt over 4 months waiting on the BECM and then charged us $200 for a new 12V battery because they never kept ours charged. Chevy corporate gave us the free OnStar and a prepaid extended warranty paperwork for all maintenance for a year. The OnStar upgrade renew just caused the horn and lights to go off continually like the car was being stolen until I had to perform a key reset myself on the door lock because the dealer service guy reset the lock to get in when the battery went dead. Also, when I took the extended warranty paperwork to the dealer to verify and see what they would cover they just said they would not accept it at all. After several calls to Chevy/GM they are looking for another dealer who might accept their prepaid service plan. It's been several months now with nothing but more BS excuses. I can't make their dealer honor their Chevy contract with me. I finally just told them I will trade this POS in for a decent brand and never own another GM vehicle in my life time. My next electric vehicle will be a Hyundai Ionic 5, the Car and Driver SUV of the year. American vehicles can no longer compete because the American dealership network no longer serves the American public's car needs. The worst buying and service experience in America is the automobile. Any other business with that reputation would be out of business. Why do we put up with it? It is as broken as our politics.

 

Most of us Volt owners have been through this same song and dance with GM promising but not delivering and dealers being incompetent or outright criminal. Our dealer had our 2017 Volt over 4 months waiting on the BECM and then charged us $200 for a new 12V battery because they never kept ours charged. [..] horn and lights to go off continually like the car was being stolen until I had to perform a key reset myself on the door lock because the dealer service guy reset the lock to get in when the battery went dead.

Wait, didn't you leave a key with the dealer? They physical key would have opened the door, dead battery or not. Maybe not having the key was why they didn't charge it....

 

Has GM fixed the issue with the BECM? Just had mile fail, will know next week how long it will take. The question is that will I be dealing with this again in another 45K, really love the car but if this will be an ongoing issue, then will probably trade it in.

 

After reading this postI am concerned with my new to me 2019 Volt w/45k miles on it. I'v only had it a few days and I noticed sometime when I put it in park, and I turn the engine off, it says I need to put the vehicle in park. It seems to cure the issue if I start the car up, put it into parkwith a little more force which seems to work. I hope I am not getting the BECM issue. My wife will be angry as hell since I convinced her the Volt is a great car and we can save money on gas. I hope it doesn't happen.

 

After reading this postI am concerned with my new to me 2019 Volt w/45k miles on it. I'v only had it a few days and I noticed sometime when I put it in park, and I turn the engine off, it says I need to put the vehicle in park. It seems to cure the issue if I start the car up, put it into parkwith a little more force which seems to work. I hope I am not getting the BECM issue.

"Shift To Park" issues aren't related to BECM at all. There's a flaky microswitch in the shifter assembly, and there's a service bulletin out alerting dealers how to repair.

 

"Shift To Park" issues aren't related to BECM at all. There's a flaky microswitch in the shifter assembly, and there's a service bulletin out alerting dealers how to repair.

I’m having the “shift to park” problem but learned from a Reddit post to pull the shifter button and flick it off. That works instantly, so far.

 

This has also been working for me on my 2018 LT. It's been very intermittent as well, there are times when it happens every day and then it can go for several days and not do it at all. I shift from D to L quite often during most every in town drive and that does not consistently cause the issue.

This is why I'm hesitant to take it to the dealer to try to get it fixed under warranty when it's not repeatable on demand.

 

The symptoms of a dying BECM are known: 6 or 12 U26xx errors, 0-1 miles on a guessometer (yes, it's always a guess, which depends on many factors) wigh full battery indicator, sudden ICE kick-ons, STP and low propulsion messages.

If you don't experience above symptoms, BECM change won't help you. Check for kWh used on a depleted battery rather than GOM numbers and if that is above 12 kWh, the battery is okay. I think you just have low temps thus a reduction of GOM numbers.