2006 aveo p0700, u0073, u0100 codes

I've had this problem with this car for along time. I'm a mechanic and have tried a new speed sensor in trans, checked grounds, and replaced the ecm. The car will run for weeks without and problems and then will set codes and the trans will default to second gear and the car clunks. I've talked to others and nobody really knows. I was thinking of trying a TCM and been told it might fix it but, don't want to spend 300 and not fix problem. I looked through this forum and did not see any other aveos with same issues. Any help would be great! Thanks

Just for giggles, borrow a buddies battery and see how it does. A week battery can cause ECM/TCM communication failures.

Are you getting the 2 U codes using a scanner that's supposed to be able to read the Aveo TCM? Do you have access to another brand of scan tool that can read Aveo TCMs? If multiple Aveo TCM readers get those same U codes, then it would make the TCM seem like the culprit. If it comes to that , how about trying a U-pull TCM for a lot less $$?

TCM not going to work. I have the same issue so far I've replaced:

TCM
Alternator
Battery
Cylinder head (With new valves)
Neutral switch
Complete engine (brand new out of the crate)

Guess what?

Same three codes are still coming up.

At a total loss as to what the issue may be.

Quote:

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Originally Posted by carguy

TCM not going to work. I have the same issue so far I've replaced:

TCM
Alternator
Battery
Cylinder head (With new valves)
Neutral switch
Complete engine (brand new out of the crate)

Guess what?

Same three codes are still coming up.

At a total loss as to what the issue may be.

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Why in the world was that engine stuff done for a P0700 generic transmission code? Once again, did anyone try to read the TCM for specific codes? I could maybe understand trying a transmission replacement, but a new engine (after trying a head) :confused:
What year Aveo do you have?

I would say this is a bad ground personally. Did you check the power supplies as well? burnt fuse block or power distribution?

But if those were checked, then I the only other thing I could think of is the coil pack. Loss of signal for RPM, puts the transmission in limp mode (2nd gear).

Quote:

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Originally Posted by avguy

Are you getting the 2 U codes using a scanner that's supposed to be able to read the Aveo TCM? Do you have access to another brand of scan tool that can read Aveo TCMs? If multiple Aveo TCM readers get those same U codes, then it would make the TCM seem like the culprit. If it comes to that , how about trying a U-pull TCM for a lot less $$?

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Yes I've used a snap on scanner a cheaper code reader and a gm tech 2 scanner and all same codes. I might look into a used one see how much I can get it for.

Quote:

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Originally Posted by petrified.rabbit

I would say this is a bad ground personally. Did you check the power supplies as well? burnt fuse block or power distribution?

But if those were checked, then I the only other thing I could think of is the coil pack. Loss of signal for RPM, puts the transmission in limp mode (2nd gear).

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I checked and double checked the grounds, there are two main points. Under the car and on the passenger inner kick panel. The car is not missing and doesn't lack power.

Quote:

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Originally Posted by avguy

Why in the world was that engine stuff done for a P0700 generic transmission code? Once again, did anyone try to read the TCM for specific codes? I could maybe understand trying a transmission replacement, but a new engine (after trying a head) :confused:
What year Aveo do you have?

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Engine was replaced due to bad compression in a cylinder.

Quote:

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Originally Posted by carguy

Engine was replaced due to bad compression in a cylinder.

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Hi, didn't you mentioned on 2-12-2014 that the engine was replaced and the code still came up?
What's the final fix?
How much you had spent all along fixing this problem? Just curious.
Did the car drive well before this engine light came on the first time?
After each unnecessary fix that you mentioned, the shop should have reset the computer to clear the error. Did the car drive well afterwards before the light came on again? Or did it drive the same way as before the wrong fix even though the computer was cleared?