[09-2LT]

Good morning all. I have a 2009 2LT 3.6 V6 with 208,000 miles.

For some background, my parents bought the car new. My mom drove it for several years and put about 120,000 miles on it. During that time, she would often get a "check gas cap" message. Multiple trips to the dealer and multiple new gas caps never solved the problem. After I bought the car in 2016, the occasional "check gas cap" messages continued and later I started getting "service ESC" or "service traction" messages. All of these messages would come and go with no change in the car's performance. Periodically, the express up/down feature on the drivers window also stops working.

Last week while pulling out of the parking lot at work, the transmission shifted very hard from first to second, the check engine light came on, and the car refused to shift out of second. Reverse worked fine but the car was locked in second going forward. No self shifting either. It was a long 45 miles home.

Google brought me here and after some reading it occured to me that every time I've gotten a service message, it's been during wet weather and it had rained the night before the latest episode too.

So I pulled all of the ECM and BCM connections, gently cleaned the pins with a small brass wire brush, and put dielectric grease on all the connections. Reconnected the battery and started the car. As soon as it shifts to second, the engine light comes on and its locked in that "limp mode" I've seen mentioned here.

After checking all the ECM and BCM connectors again, I started randomly checking wires and connections under the hood. This led me to a box between the battery and the firewall with a large connector plugged into the front of it and what look like 4 brake lines running into the top of it. I have no idea what this thing is or does, but the connector was full of dirt and corrosion. I cleaned it and added dielectric grease thinking I had solved the problem. I was wrong. The car still goes into limp mode as soon as it shifts to second. But on the flip side, the express up/down on the drivers window started working again. So theres that.

If anyone has any ideas, I'm all ears. I've reached the point of giving up and taking it to a shop. All thought and comments greatly appreciated.

Thanks.

 

[09-2LT]

That module with the brake lines is the ABS module. There is nothing wrong with cleaning that connector, and everything right.

Under the console is the BCM. If you take of the cover from the driver's side you can access another connector that isn't quite so obvious.

There is another control module connection between the battery and radiator support if you didn't find it yet.

Since your family has owned it since new, do you know if the trans fluid has ever been serviced? If not, you may want to consider it.

The Service ESC and/or ESC Off messages can plague you with their incessant warnings, but for my 2011 3.6L, it's most likely the SAS (steering angle sensor) located on the steering shaft under the dash. I just haven't gotten around to having it fixed. It'll come on almost daily for a period of time, then be off for months at a time as well, which suggests to me that it's just a dirty or corroded connection.

Another item to consider is the ECT - engine coolant temp - sensor. If it's bad and the temp gauge climbs pretty high, it could be signaling an overheat condition to the BCM that then tells the ECM to go into Limp Mode, but that's just a theory. I had my ECT fail 2 years ago and it kept driving normally even after popping a message that it was overheating. I pulled over, checked it all out, then continued. Only 5 miles later and it was in Limp Mode. The t-stat had actually failed in a closed position and the ECT was properly indicating the condition. The following week I made a round trip of 1500 miles after replacing the t-stat, water pump, most of the hoses, and cleaning the overflow reservoir. Not one problem, and it had only water in it (in case I needed to open it up again and keep from losing expen$ive coolant).

I thought maybe that was the ABS module. I'll look for that connection behind the BCM and try it next. I had issues with the car running hot last summer but a new water pump fixed that. I forgot to mention that I replaced the alternator last year too. My mother had the car serviced religiously every 3000 miles by the dealership the entire time she owned it but I dont know if they ever touched the transmission. My mom is one of those ladies that walks into the service dept for an oil change and says "just do whatever you think needs done" so theres no telling what they did or didn't do.

 

[09-2LT]

This connection looks like its had transmission fluid in it. Any thoughts on how to clean it without damaging it?

 

[09-2LT]

Contact cleaner after disconnecting all battery cables. Then plug it in and unplug it several times to burnish the terminal contact surfaces, then use dielectric grease to help reduce the effects of environmental changes.

Worked like a charm. Running and shifting fine now. I'm not going to take it too far from home for a few days and see how it acts. We have a pretty good local transmission shop. I may take it in and have them check it over just to be sure.

 

[09-2LT]

Well, it ran fine for a week. Then last night on my way to work, boom. Engine light comes on and locks into limp mode. Time to call the repair shop I think.

 

[09-2LT]

Finally got an update. It is indeed a bad sensor. Thats the easy part. This particular sensor is inside the transmission. The old guy who owns the shop says it's a 2 day job because they basically have to disassemble the entire front of the car and he's not sure when they can fit it in their already overbooked schedule. His son, who is the head mechanic thinks he can get it done in a couple hours (squeezed into the schedule) by lowering the cradle just enough to get to the sensor cover.

To be continued...

 

[09-2LT]

Picked the Malibu up today. $450 out the door and we move on until next time...

 

[09-2LT]

Picked the Malibu up today. $450 out the door and we move on until next time...

Well, she lasted 2 weeks. Driving home from work the other morning, one loud clunk, and the speedometer died, the outside temp in the display blanked out, and the transmission locked into 3rd gear. My local shop says its another electrical problem in the transmission but they would rather not mess with it when we have a pretty good transmission shop just down the road. Here we go again...