My car will not start

2007 CHEVROLET COBALT
48,000 MILES • 4 CYL • FWD • AUTOMATIC
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ERICSCHROEDER
  • MEMBER
  • 4 POSTS
The battery drained when the lights were left on overnight. so I jump started it and it fired right up. Later in the day I tried to start it and got nothing. I got the battery tested and it was fine. I took the starter out and got it tested and it was okay. We hooked up a scanner to it and we got "U0100 lost communication with ECM, PCM a". Does this mean I need to replace the ECM? I am getting power to all of my lights and stereo. Any help would be appreciated!
Sep 26, 2009 at 6:23 PM
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DOCFIXIT
  • ✓Experienced Mechanic
  • 18,828 POSTS
This sounds like you had a voltage surge when jumping the battery that weakened a fuse did you check them all? Here is a guide to help us guide started:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the diagrams (below).

Please let us know what you find.

Cheers, Ken
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Jul 17, 2018 at 4:15 AM
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ERICSCHROEDER
  • MEMBER
  • 4 POSTS
We tested the small wire at the solenoid and it was not getting anything with the key on start. What does that mean? Thank you for responding also!
Jul 17, 2018 at 4:15 AM
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DOCFIXIT
  • ✓Experienced Mechanic
  • 18,828 POSTS
It can mean the system is not seeing the initiation of the ignition key.
Jul 17, 2018 at 4:15 AM
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ERICSCHROEDER
  • MEMBER
  • 4 POSTS
That would give a u0100 code?
Jul 17, 2018 at 4:15 AM
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DOCFIXIT
  • ✓Experienced Mechanic
  • 18,828 POSTS
Yes, if fuse ignition switch/PK3 in BCM located under center dash right side console.
Jul 17, 2018 at 4:15 AM
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ERICSCHROEDER
  • MEMBER
  • 4 POSTS
I checked the fuse and I replaced it with a spare. Now the car starts and runs great Thanks 2Carpros, I love this site.
Jul 17, 2018 at 4:15 AM
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