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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
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?
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).
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.
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.
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.
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.
Great to hear. How much of a pain was it to replace?
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.
Glad it was such an easy fix, and thank you for posting this information :thumbup: 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.
Thanks avguy, it was your tip that found the TCM code (P0722 in this case) that nailed the problem, without taking a risk of messing up both cars lol. With some luck I should have the orange car running this weekend.
I spoke too soon apparently. Three days and almost 100 miles on the new speed sensor, and the light is back and limp mode came on. However it is not as bad, rarely does it but still same codes popping up. Ordered a used TCM to try next. They list the ECM as an option but I would think that would show other symptoms. I may be dealing with multiple problems.
Update: Still getting same DTC's with new speed sensor, and even does it with a different 'known good' TCM. So ruled out the TCM. Even the U0100 'network communication error' pops up as I drive it. So frustrating. I have run out of things to replace, so it may be going to a shop next. I am just dumbfounded. &^$%#
I checked for 12v at the OSS connector pin, checked it at the TCM connector, wiggled the wires, etc. Solid 12v signal. So if it is harness/wiring related I can not duplicate the problem by shaking wires. I have followed the tis test procedure and still get the same result. I even thought about 'hot wiring' power to the connector but no sense in butchering the harness. I am totally at a loss on this.
Looking at the wiring diagram, that sensor and the ECM share a circuit, so that seems to be a smoking gun. Have you checked their common ground - G103? IIRC it's located at the starter mounting bolt.
To be honest I glossed right over checking grounds aside from the one at the fuse box near the battery. I will chase this circuit down and see what I find. Again - thanks for the tip avguy.
Update: Found G103, (down on the bottom starter bolt with a gang of other wires and the ground cable. ) Pulled them off, everything was clean, so I cleaned them with contact cleaner and scuffed them up a bit, and tightened. Seemed to have good ground where I checked with a light clipped to the positive post. So grounds seem to check out ok. Still getting same codes however. I saw a splice 201? On the diagram, but was not able to find the splice. Off to the dealer next week, I am still stumped.
Update: Passed on the dealer, took it back to the shop that remedied the air bag light. No matter how much I drank, could not psych myself up to go to a dealership lol So right now the verdict is the ECM, they did the same thing I have done multiple times (cleaned the connectors, and cleared the codes) and the classic story "it ran great at the shop" and would not go into limp mode this morning for the mechanic. So next visit will be a new ECM more than likely.
After about four trips to the shop, they are now on the same page. They had me order the new ECM, so I went with the Delco OE unit rockauto sells. We should hear something today, and I REALLY hope this puts this issue in the past. Good grief lol
sounds like fun. I bought a used em to try to fix my no start issue, and it didn't work. hope this works for you.
Too much fun apparently, the shop called and they are bailing out, and have referred the car to a local GM dealer for the relearn procedure. Took a month to realize they were in over their heads.
when does the ECM come?
It landed at our door Monday. It goes to the dealer Friday morning with the car for install.
Ok got the car in on Friday morning, new ECM installed and was able to pick it up a couple hours later. They cleared the codes and due to the half day holiday schedule the tech was not able to test drive it. So I get about two blocks from the dealer, and just like a ghost in the machine, MIL light's up, and right back into limp mode. Oh that was a fun moment! So dealer is closed by then, so I just suck it up. Once I got time I went over all the schematics for the ECM/TCM, G103, power feeds, grounds, etc. I noticed one connector C101 that I had missed when I was checking the harness a month back, and everyone else may have missed as well, it is down under the coolant tank, just getting to it was a bit of a challenge. It wasn't dirty or corroded, so I cleaned it with q-tips and cleaner, and silicone greased it. It may be going back to the dealer, but since I cleaned that up the U0100,P0700,U0073 are not popping up every few blocks. Who knows at this point.
Update: I think five months of no MIL, no limp mode, no anything is a sure sign C101 was in fact without a doubt the actual CAUSE of these errors. - Maybe make this one a sticky?? I think my last post was not clear since this was such a long drug out problem, but I attest it has been resolved, not by new ECM, not new TCM, - but C101.
Where is the C101 ground on a 2010 Aveo LT? I cleaned 2 by the battery and ECU but still getting the P0700 and U0100 codes.
On a 2010 I couldn't tell ya. If you can get access to the TIS wiring schematic, it will show the locations of all connectors. This set of codes indicates a faulty connection on the CANBUS between the PCM/ECU and the TCU. Find this circuit, and check ALL connectors along the circuit. One should be dirty/corroded, or a loose/broken wire. I lost access to the TIS library sometime around 2019, so I can't look it up for you. Sorry.Quote:
Originally Posted by copper
Best of luck, I know this one stumps a lot of techs.
Thanks 06T200, Ill keep looking!Quote:
Originally Posted by 06T200