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So i have the yellow lock light pop up occasionally on my dash & not all the time but a single chime followed the the whole cluster goes haywire for a second then back to normal, any ideas?
 

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OMG mine just started doing this. I was hoping for answers here. I saw on another Chevy Forum that this happens a lot but no one had a solid solution as of yet. One person has tracked it down to the power steering motor, or the harness leading to it.

It happened to me twice last weekend. Car chugged, gauges went wonky and then back to normal. Power Steering popped up on the screen. I let the car sit for a few hours and it didn't do it again. I had some other issues anyway so I dropped it off at the dealer who (of course) said they couldn't find anything wrong. I picked it up yesterday afternoon and it seemed fine... until this afternoon. I can't tell if my power steering actually went out or not, as I was parked. The fuel gauge went wonky and the Low Fuel warning came on. Then the gauge went back but the light stayed on.

This car is really starting to scare me. I mean I was gonna sell it anyway, but who's gonna buy a car that needs an exorcism? Guess I'm stuck with it for now...
 

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Don't panic. Your Cobalt shows all the signs and symptoms of loss of GMLan. 2 things commonly cause this and both are easy fixes. Most common is corrosion within the contact surfaces of P1 and/or P2 of the BCM block, so disconnect battery then disconnect these 2 connectors by pulling the levers on the blue / grey connectors plug and unplug a few times (5 or 6) to clean the contacts. Then take your car for a spin and see what happens, if problem disappears for a year you know where the problem lies and next time you may want to add dielectric grease to help keep the moisture out. If the problem comes back then you might want to look at the top left hand fuse (red 10 amp) of the BCM block since it has a tendency to pit, Just replace outright.
 

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Would a bad connection also cause the weird shifting? It's an automatic.

I also had a stored history of U2105 and U2107, but I never had a scanner handy when the dash light was still on to know if it was current.
 

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U codes are communication codes which is exactly what you are experiencing with lost of GMLan. This is the communication link between all CPUs including the TCM, so yes hard shifting is also a symptom. Had this problem with the 07 almost 2 years ago and it hasn't come back. I can't tell you which of the 2 was my problem since I did all of it at once.


U2105 Lost Communications with Engine Control System- BCM, EBCM, PSCM, TCM
U2107 Lost Communications with Body Control System- EBCM, ECM, IPC, PCM, PSCM
 

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It is not possible for me to thank you enough, sir. I'll go poking around in there tomorrow. I just got my car back from the shop yesterday and I didn't wanna keep dropping fat stacks of cash on stuff I can try to solve on my own first.
 

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The 2 big connectors were clean as a whistle inside. No sign of corrosion, so I went ahead and replaced the 10 amp fuse. It wasn't pitted, but was a little discolored.

The car only wants to do this about once a week, so we'll have to see if this issue comes back. It's my daily driver and I'm usually alone in the car, so don't want any issues!
 

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Very seldom is the corrosion visible though unless it's green. Hope you still unplugged and plugged them a few times just for the sake of argument later.
 

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Let us know if the problem comes back, you can tell the garage later how much it cost you for the repair if the problem doesn't come back. lol
 

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if it continues to act up, should I clean the connections with compressed air? Not sure why I didn't think of doing that before. Transmission still seems a wee bit "off", but no dash lights yet...
 

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I use contact cleaner and dielectric grease and it's been a year and a half.
 
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