U0100, and P0700 popping up

[06T200]

Been getting a P0700 intermittent (Trans code) with no clues as to why this week. Then this morning on the way to work I saw this pop up about 12 times - U0100, so I think I have some dirty connectors I need to clean. May be a coincidence but the keyless locks stopped working as well at the same time. Will scan the BCM for codes tonight with the laptop. - It's always something lol

[06T200]

Update: Last weekend I pulled the connectors from the ECU under the hood, and from the TCU under the dash. Cleaned them up with some CRC 2-26, and did not find any corrosion or dirty contacts, so I plugged everything back in. While I was doing this I had the battery disconnected. I also disconnected the DRL module while I was under there. - Cleared the codes, and took it on a test drive. Drove fine for about 15 miles, no codes, nothing. Even drove a few trips after that fine. Then on Monday I drove it to work, and now they are back, same as before. Oh joy!

So this makes me think the TCU may be flakey, even though it seems to work fine when it wants to. I have read that to replace the TCU the replacement needs to be programmed. But not sure why. Has anyone ever swapped out the TCU with a good known TCU? I ask as I have a good working TCU in my other 06, and I would like to just swap in the good one to see if that makes it happy. Then I can blow the cash on a new TCU if that is the problem. Has anyone just swapped them out between cars to test? Does anyone know why the TCU would need programming, other than to make sure it has the correct code? Will the TCU know it is in an LT model, and not an LS model?

[avguy]

Before doing anything else, you might consider taking it to a transmission shop to have the TCM code(s) read, or any other place that has a TCM-capable reader. The more specific TCM codes may pinpoint the exact problem.
And its also possible that the U0100 is another, separate problem (the typical P0100 doc only mentions ECM-related items).

[06T200]

Thanks avguy. I may get to that point before too long, but I like learning new stuff when I can. I am still determined to 'DIY' using an ELM interface, but was unable to find the node address of the TCU last night, apparently they didn't use the 'standard' $18 module address, so I have some more exploring to do in the $19-$1F address range. According to Aisin's manuals they do follow the DTC coding standards, so if I can just find it I should be able to pull the codes.

[06T200]

Finally made it to see my trans guy and had him pull codes for the trans issue. He pointed to the OSS speed sensor down under the master cyl. Since it had a code for this. So sourced one of those and will try that next, and go from there. GM just calls it a 'gear #93741426' so there was some confusing info in the parts diagrams, but I found one at rockauto but listed for the 06 Aveo5. go figure lol only the input ISS sensor is listed. Will keep ya posted.

[06T200]

Here is my alleged MIL culprit, the OSS speed sensor, here is some info to note on this critter, also found a test procedure and pinouts. Might come in handy for others with output VSS codes.

Edit here is a link to the test procedure online: ftp://213.141.147.82/Lachetti/Chevro...2_5A02.en.html

Scroll to about mid section, should see the voltage pattern to look for.

Wasn't able to attach a pdf version, but this is the same test more or less.

[06T200]

Follow up: Day three on a new speed sensor and no codes, trans is shifting fine, no 'limp mode'. So thus far, looking like it was the OSS. Which has me stumped since there has never been any issue with the speedo, but knock on wood it's running great.

[Daox]

Great to hear. How much of a pain was it to replace?

[06T200]

Not bad Daox, had to get it from under the car, 1 12mm bolt, and some light taps and it popped up, then the fun part was getting my hand on it to maneuver the unit out of the trans case, it took a bit of finesse to get it out. New one slid in easy. In all about a 30 min job.

[avguy]

Glad it was such an easy fix, and thank you for posting this information It will certainly help others down the road. This is the type of thing that folks get taken to the cleaners on. It would probably be really disturbing to know the number of transmissions that get replaced when the actual problem is something as easy and simple as a sensor, computer, or solenoid.