U0100 - Lost Communication With Engine Control Module - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 2 (permalink) Old 02-13-2017, 03:44 PM Thread Starter
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U0100 - Lost Communication With Engine Control Module

Hello my new friends

I have here a 2008 Chevy Cobalt that is throwing a U0100 code. I am not getting crank when turning the key. Also the fuel gauge doesn't move when in the 'on' position and also usually see 'power steering'. The results vary when I turn the key to crank position. Sometimes the dash won't change. Right now when I crank all the lights go out. It's almost like a bad ground. I have manually grounded the chassis of the ECM to the chassis and engine grounds, but no luck. I have taken the ECM out and looked at the connections in which they look fine to the naked eye.

I found two fuses under the hood for ECM. One is a 15 amp fuse marked ECM and another is a 20 amp fuse marked ECM/PCM. The 15 amp fuse tested fine and I am getting 12 volts from the left leg of the fuse. However the 20 amp marked ECM/PCM is not getting any voltage at all. These tests was done with the key in the ON position.

I have checked the battery terminals and they look fine. I even unbolted them and rebolted them.

I have not taken the ECM apart yet to look for burnouts. I wanted to diagnose this 'no voltage' to the fuse before doing so.

Anybody have any suggestions or comments?

Here is the VIN details in case it helps.
Vehicle Identification Number VIN 1G1AL58F387310060

Thanks a bunch

---------- Post added at 11:44 PM ---------- Previous post was at 10:17 PM ----------

I think I found my answer
https://www.yourcobalt.com/forums/pro...ighlight=u0100

This is the exact same issue I am having even with the no voltage to the ECM/PCM 20 amp fuse.

I tried to send that user a message but I don't have enough posts yet to do so.

In the very last post on that thread was a post by Coby7. https://www.yourcobalt.com/forums/1265538-post19.html
It seem the joshsaville had bought a used ECM from a salvage yard. I see them on ebay saying "programmed for your VIN".
I am trying to figure out if that is the route I should go and confirm that if I buy a non programmed one for cheaper that I would
need to get it programmed since I don't have a tech2 scanner.


This is the private message I attempted to send to joshsaville.

"
Hello friend. I was going over your thread https://www.yourcobalt.com/forums/pro...ighlight=u0100
I am having the identical issue as you.
My 15 amp ECM is getting power but my 20 amp ECM/PCM is not getting power just as you mentioned in your post.
I see you got a used ECM which is what I am planning on doing. It appears you got one used that was not programmed specifically for your VIN.
This would be the case if you got it from a salvage yard.
I am now inquiring from you what you had to do after you got it installed?
I see it was throwing a crankshaft error. p0315: Crankshaft Position (CKP) System Variation Not Learned
What did you do to resolve this?

I can get used ECM from ebay that are pre-programmed for my VIN. But not 100% sure if I have to do that or not or it will re-learn by itself.
Any help is greatly appreciated.
"

Thanks,
Jeff
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post #2 of 2 (permalink) Old 05-02-2017, 10:30 PM Thread Starter
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I ended up buying a used ECM/PCM from ebay that was pre-programmed to my vin with the latest flash updates.
Worked like a champ.

The only thing not resolved is the 0315 crankshaft needs to be relearned. I believe this needs to be done with a tech 2 scanner which I don't have.
The code does not affect anything though.

ENGINE COMPUTER PROGRAMMED CHEVROLET COBALT 2007 2008 2009 2010 12612397 OEM | eBay
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