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Discussion Starter #1
The shifter, 2007, auto trans , locks in park. Seat belt on, foot on brake, doors locked, sitting snug in the seat, it locks in park when I tried to go. I turn it off and start over, sometimes it works fine, other times it locks in park. Tried lifting my foot off then on the brakes, toggle the lock switch, lock unlock the belt, sqiggle in the seat to make the switch click. Nothing makes sence, then all of a sudden it unlocks and I go.
I don't have a code reader right now and I thought this might be a problem someone else experienced here.
I'm pretty sure it has to do with one of the switches not sending or working correctly.
Any imput on this is welcome, Thanks.
 

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I never had this problem with any of my 3 Cobalts but did with my wife's G6. Turns out they have the same BCM and in my wife's G?'s case I just removed the 2 blue/gray connectors ( P1 & P2 )from the BCM sprayed them with brake cleaner, let them dry, added a bit of dielectric grease and voilà! It hasn't acted out since, this was 2 winters ago.

 

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Discussion Starter #3
Thanks Coby7, I'll give it a try. This was weird as only intermittent electrical problems often are. While I'm at it I'll check as many connectors as I can find. This is Florida and humidity has been known to cause problems with corroded connections.
 

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Discussion Starter #4
So I poked around the engine bay power/fuse box and found it to be loose. Looking for a way to tighten things up I caused a spark from the positive battery treminal to the regulator or whatever. Now the display on the speedometer is flashing, service traction and power steering. The temp reading and most other information is gone also. Tried disconnecting the battery positive in the trunk to reboot the system but everything is the same.
Tomorrow in the light I'll check for blown fuses. I really need to pick up a code reader before I really make a mess.
What a day........
 

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Yeah you probably blew a fuse. Report back...
 

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Wait, little off topic, but the g6 uses the same bcm as cobalts? I thought they were different and the reason the g6 shifter couldn't be made to work in the cobaltc
 

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Wait, little off topic, but the g6 uses the same bcm as cobalts? I thought they were different and the reason the g6 shifter couldn't be made to work in the cobaltc
Based on Rock Auto, no, they don't. It shows the G6's BCM as being in the Malibu and Aura, which makes more sense.
 

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They have a different firmware but are electronically the same. Physical appearance is identical.

 

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Well yeah, why would GM spend extra money to use a different module housing - especially at that time. :laugh:
 

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Discussion Starter #10
Alright , I really screwed up. The part I grounded the terminal to is the TCM trans controller, controls the shifting of the automatic. Right now the car is stuck in low gear. Auto zone read the codes and U0101 lost communication to TCM came up. Tried to reboot by disconnecting the battery again, no good. I'm going to have to get this part now, we need the car now.
 

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Changing the TCM might not work for you. You need to find the problem, did you check the GMlan fuse in the BCM if you lost communication. It is called the ECM/TCM fuse.

 

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Discussion Starter #12 (Edited)
OK , I don't know what or where the BCM Is. I have the power box in the engine bay.
I put this link up so you can expand the pics.
https://drive.google.com/file/d/1kbKBqx_2klonSHQyqpjsAshwl1O19hu4/view?usp=drivesdk

https://drive.google.com/file/d/1R61sz0qS9V5Jr0f5jYle6sDkagqJkHAD/view?usp=drivesdk

You can see the upper right there is a nut missing from the stud holding the coolant tank and the fuse box. When I lifted it the positive post at lower right contacted the TCM ,looks like a metal bar ,Sparks flew and real trouble started, it's locked in low gear.
Searched all over town except NAPA, nobody has the part, and can't get it. I can find it online but shipping will take whatever it takes. NAPA has it on the store site I hope they have it in stock, Chevy has to order it.
😵
 

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You haven't listen to me from the first post. If you would have read correctly you would never have gone under the hood. The BCM fuse block is to the right of the center console on the passenger side. Your TCM isn't the problem

Re-read twice what I've been posting.



 

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Discussion Starter #14 (Edited)
Thanks Coby7, again. Found the BCM panel and will proceed in the morning. All of these acronyms take some time. I'm still new to the car, the book calls it the interior fuse panel.

Edit ; I would have tried to find out why the engine fuse box was loose anyway.
I really didn't know what the BCM was and was basically looking for something that looked like the pic you put up.
 

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I really didn't know what the BCM was and was basically looking for something that looked like the pic you put up.
The underhood fuse block locks nothing like the first picture I posted. I like to help but......
I've owned 3 Cobalts, none had the nut on that stud.
 

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Discussion Starter #16 (Edited)
I appreciate the help. I was lost at first, I should have asked where the BCM was and not gone poking.
So that engine fuse box should be kind of loose, I'll let it be. Thanks

edit;. add panic to the mix😵
 

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You can see the upper right there is a nut missing from the stud holding the coolant tank and the fuse box. When I lifted it the positive post at lower right contacted the TCM ,looks like a metal bar ,Sparks flew and real trouble started, it's locked in low gear.
I think I know what you did now, you will not need a new TCM. If the boost post touch the heat sink of the TCM you probably just fried the ground wire that goes from the TCM to the engine block. If you put an ohm meter between the TCM heatsink and the engine block you should read close to zero if not try grounding the TCM to a known good ground and take it out for a spin. Here is where the TCM grounds to on the transmission and engine.


 

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Discussion Starter #18
Coby, Yep, the ground wins the prize ! Added a 12awg from the engine ground to the case of the TCM. Took it for a spin and shifting fine. Shut it down and when I started again all the warnings cleared and the outside temperature and the trip mileage restored.
Now I'm back to square one with the shifter locked in park. The car will shift if I wait a bit.
This ain't over yet so stay tuned.
Thanks for all of your help, complicated issues can be difficult to communicate in a forum like this, but it all works out fine.
 

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Go back to post 2 now.
 

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Discussion Starter #20
I will now proceed with post #2 in an orderly manner, avoiding any charged posts or cables.

I ran some errands and I have noticed a solid click at the shifter lock as I touch the brake, more so than previously. Makes me wonder if the ground from the TCM was part of the locking up issue, maybe corroded. Anyway all is working well, back to normal. I'll be back.
Thanks again !
 
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