U0100 communication problem that my mechanic could not pin point the reason after 2 trials.

CPW06516

MEMBER
2006 CHEVROLET AVEO
1.6L
4 CYL
2WD
AUTOMATIC
45,000 MILES

I have a Chevy Aveo of year 2006. The engine light came on a month ago, and the engine immediately hesitated (acted as if I was applying the brake). I took it to the shop, they got the code (u0100) and all those details, worked on it, and at the end of the day told me that all places possible for the communication problem they had looked at and couldn't find anything wrong. It happened again this Monday. They had it for the whole day and still couldn't figure it out.

10 Replies

JACOBANDNICKOLAS

MECHANIC
108,179 POSTS

That code indicates that the ECM and TCM are not communicating. Most common causes are:

Faulty TCM
TCM harness is open or shorted
TCM circuit poor electrical connection

I don't know what they checked, so it makes things harder for me. Can you ask them to explain what was done?

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Wednesday, July 30th, 2014 AT 9:33 PM

CPW06516

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Thanks! Will call them tomorrow to find out.

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Wednesday, July 30th, 2014 AT 9:39 PM

JACOBANDNICKOLAS

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108,179 POSTS

I'll look for your reply.

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Wednesday, July 30th, 2014 AT 9:43 PM

CPW06516

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Hi, I just found online a GM warranty document saying that ECM and TCM are warranted for 8 years / 80K miles. My car should still be within the warranty period. Any shop that's authorized to perform warranty work must first prove that it's the TCM fault causing the problem before getting warranty coverage for the TCM replacement work, right?

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Wednesday, July 30th, 2014 AT 9:44 PM

CPW06516

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I just talked to the mechanic. He said that he's checked every wire and they visually looked in good shape, the connectors looked good and tight, and no ground open. He said that the next he plans on doing in sequence are as followed:
1. Use a temporary power wire to connect the circuit and stop using the original power wire. If that fixes the problem, then he will replace the power wire for a permanent fix.
2. Repeat #1 on the ground wire.
3. Replace the connecting pins into the TCM and the ECM.
4. Replace the TCM
5. Replace the ECM

This is a trial and error approach. If #1 does not work, try #2. If #2 does not work, try #3. He will keep on until he's done #5. When asked what's next if #5 still does not fix the problem. He gave no answer. And he said he's about 50% confident that one of these 5 trials will fix the problem.

What's your opinion? Thanks!

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Thursday, July 31st, 2014 AT 10:54 AM

JACOBANDNICKOLAS

MECHANIC
108,179 POSTS

To check the wires, he doesn't have to replace them. He just needs to test them for continuity. That will tell him if there is a problem.

Listen, based on your findings, I would take it to a chevrolet dealer. Your present mechanic will most likely find the problem, but how long will it take?

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Thursday, July 31st, 2014 AT 3:00 PM

CPW06516

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Thanks for the inputs. I will wait until the check engine light comes on again and take it to the dealer.

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Thursday, July 31st, 2014 AT 3:19 PM

JACOBANDNICKOLAS

MECHANIC
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Let me know how things work out for you.

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Thursday, July 31st, 2014 AT 9:23 PM

ALBERT455

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The engine check light is on.I tried to scan the the car but the only result I get is the exterior and interior connections but not the engine. And I have to get the code from the engine. Is at the mechanics shop and this is the information I got from him. Can you please help me out

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Saturday, June 3rd, 2017 AT 1:40 AM