Won't crank or start - U0100 Code

Tiny
JAZZARO1
  • MEMBER
  • 2005 CADILLAC STS
Computer problem 6 cyl Two Wheel Drive Automatic 72000 miles

I have a car with 3.6L V6 and 72k miles. When brake and Start Button are pushed the dash goes black, but interior lights stay on, and will not crank/start at all(no clicking, no nothing). After 10-15 seconds, dash lights come back up as if car is running, but engine has not started. All interior lights and gauges appear to be working properly. Tried jumping the car, no go. Took the battery to be tested and it tested okay but I purchased a replacement just to be sure as the dealer had replaced the battery under warranty just 2 years before when this happened. The car still will not start. I checked the codes and only get one trouble code, U0100 "Lost communication with Engine Control Module/Powertrain control module A." I have seen several other posts on other sites regarding starting problems, but curiously, no one has posted their final resolution. Thanks.
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Tuesday, June 8th, 2010 AT 3:13 PM

13 Replies

Tiny
KEN
  • ADMIN
Hi,

U0100 communications been established with the ECM (data display and codes from the ecm itself) I know you mentioned jumping the vehicle, but has it experienced a low voltage condition. It sounds like the battery is no good or you have dirty battery cables.

Try this test.

https://www.2carpros.com/articles/car-battery-load-test

Please let us know what you find.
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Monday, April 11th, 2016 AT 2:03 PM
Tiny
KEN
  • ADMIN
The user never got back to us which is a shame, the fix would have helped a lot of people. If I were to guess I would say it was the BCM itself has burned out which would cost some $$ so they might be mad about it and that's why they don't get back or it was an easy battery replacement problem.

IF you find out please let us know it would help many others.

Best, Ken
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Thursday, September 29th, 2016 AT 9:35 AM
Tiny
MRHARLEYMAN
  • MEMBER
I have the exact same problem. Have checked all fuses and they are fine. I had been driving the car the day it started the issue. Came home shut off car, went back outside to leave and it wouldn't start. Gauges came on but went out after I pushed start button. Then it started on its own. Then it wouldn't start again. Replaced battery still no start. Guess I'm going to have it towed to the dealer. My car only has 95,000 miles on it. I'm second owner and purchased it when it had 33,000 miles. No other problems to speak of.
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Sunday, November 20th, 2016 AT 10:27 AM
Tiny
KEN
  • ADMIN
That is weird, no one has gotten back to us on this problem. It sure sounds like a BCM to me but with having the car in front of me it's tough to tell.

When you find out can you please get back to us so it will help others?

Best, Ken
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Sunday, November 20th, 2016 AT 10:42 AM
Tiny
MRHARLEYMAN
  • MEMBER
Yes, I had it towed to the dealer yesterday, said it would be a few days before they can get to it.
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Thursday, November 24th, 2016 AT 7:02 AM
Tiny
KEN
  • ADMIN
Sounds good! I an extremely interested in what happens.

Best, Ken
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Saturday, November 26th, 2016 AT 7:09 PM
Tiny
KEN
  • ADMIN
Hey,

Did you ever get the problem fixed?

Cheers, Ken
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Monday, June 5th, 2017 AT 6:12 PM
Tiny
3DALE3
  • MEMBER
Ken,

I am jumping in here, a year later, with the same problem. Did anybody ever respond with a solution, I just joined 2CarPros so I hope we can help each other.

Thank you, Dale
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Sunday, April 22nd, 2018 AT 4:26 PM
Tiny
KEN
  • ADMIN
Yes, people are not getting back it looks like but when I re-read this post it sounds more like the PCM has gone out because that is what the code is for.

Please check all fuses then I would try to find a used PCM and plug it in, sometimes they work and other times you need to have it programmed for about $130.00 at a shop

Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Monday, April 23rd, 2018 AT 12:32 PM
Tiny
3DALE3
  • MEMBER
Hi Ken,

You also replied to a long description of my symptoms so we might have two threads going on here for the same problem. There you suggested trying another PCM. Anyway, I am seriously thinking about buying a Pass-Through device and getting a temporary subscription to the GM software ($55.00 for three days) to flash the modules. The problem is the prices for the Pass-Through devices are all over the map, $700.00 to $2,300.00. I cannot figure out if the $700.00 version will successfully communicate with and flash the modules that I need to do. Any pearls or wisdom here?

Thanks, Dale
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Tuesday, April 24th, 2018 AT 2:44 PM
Tiny
STEVE W.
  • EXPERT
The only after market J2534 device I trust is the Drew Tech. Unit. It is repackaged by many companies including AESWave, AETools, and even Autel.
I opted for the Autel 908P with the wireless J2534 device. $2,400.00 to get the pass through and a new scan tool.
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Tuesday, April 24th, 2018 AT 6:21 PM
Tiny
3DALE3
  • MEMBER
The "new scan tool" you're referring to is the Autel tablet, correct? Then the J2534 unit is a separate pass-thru device, correct?
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Tuesday, April 24th, 2018 AT 6:45 PM
Tiny
STEVE W.
  • EXPERT
Yes. Except Autel uses the pass through device as its interface to the vehicle as well. Or you can get the scan tool with a standard dongle and then the J2534 unit as an add on.
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Wednesday, April 25th, 2018 AT 8:38 AM

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