Help - Codes - U0100 & U0073

[olskool]

Replying to your post - that's great information. We were supplied with everything from a supposed LS Swap person. He has provided some technical assistance trying to help but he is to the point he has no idea. That's where we are at. We have done 4 of these LS swaps with no issues on the 4 - until this one.... Nothing makes sense that is happening. It's a stand alone harness that was sent with the PCM/tune from this individual. You are correct, I do not understand what's going on. No disputing that. That's why I'm here asking the question. You might have helped solve it. Part number on the ECM is 12614085 which has 1 black and 1 grey plug

[olskool]

Here is a picture of the PCM backside with numbers and the 2nd pic is a online picture of what it looks like with plugs

[olskool]

Here's the file:

[GHuggins]

Says 07 Tahoe yet you said everything was from a 18 express. As Shrek pointed out - OS and internal Vin mismatch. Whomever sold you the kit should have known this. Now to fix it - you'll probably wind up having to get a tcm/valve body for the corresponding Tahoe and install that into the transmission and then flash both to the latest greatest via tis2web.

[olskool]

Yes that is correct. That is what he sent - I didn't have much to do with that purchase as it was my customer who took care of it all with him. He sent everything as an entire kit. He said this is everything we need to do it. Once we got some of the tuning done it started up and ran good, not perfect but ran decent. Took a while to get it run right & in my opinion, I don't think it's running the best it can be. Just a gut feeling on that. My technician has questioned a software issue etc and that maybe because of the OS/Internal VIN not being right. He's is very good at this and he has been stumped. We do have some fuel trim issues that aren't right either. Can't figure any of that out to date and it's been very frustrating. I'll be even more frustrated if this was something that wasn't going to work from the beginning. I've wasted countless hours on this then. So my question is, can I switch the tune to a manual transmission in HP Tuner and then get a stand along TCM module/control pack. Is that possible. Or if I have to get the corresponding Tahoe Valve Body/TCM - where can I do that? Sorry, I'm used to carburetors and old school automatics. This has been quite the learning curve. Thanks for your help

[gtstorey]

Regarding adding resistors on the communications bus - this is completely unnecessary as long as the ECM is connected to the communications bus - it has the requisite internal resistor.

I'm sure everyone is correct about the mismatch but at what point is the 2nd resistor required? In my swap (still running a BCM, TDM and ECM) I had very iffy communication when I removed the EPS that had 2nd resistor just prior to the DLC. Car would occasionally start but would barely idle, various scanners would sometimes connect but not always and would give U codes when they did. I don't remember the actual code numbers though. Added a 2nd resistor in parallel just prior to the DLC and everything went right back to normal. It definitely acted like a "noisy" signal issue so may just be dependent on how much stuff is bundled in with the data wires, how close they run to things that may cause interference and how far apart the various modules are.

[TheMechanic]

ECM is a 2007 E38
63lb

[Shrek]

I'm sure everyone is correct about the mismatch but at what point is the 2nd resistor required? In my swap (still running a BCM, TDM and ECM) I had very iffy communication when I removed the EPS that had 2nd resistor just prior to the DLC. Car would occasionally start but would barely idle, various scanners would sometimes connect but not always and would give U codes when they did. I don't remember the actual code numbers though. Added a 2nd resistor in parallel just prior to the DLC and everything went right back to normal. It definitely acted like a "noisy" signal issue so may just be dependent on how much stuff is bundled in with the data wires, how close they run to things that may cause interference and how far apart the various modules are.

In a custom vehicle (Hotrod) using a Gen 3 PCM, or a properly matched Gen 4 / Gen 5 ECM and TCM combination, there is no need to add a resistor to the communications bus. Most aftermarket LS / LT wiring harness manufacturers do not add a resistor to their wiring harnesses.

I do not know how you would accurately determine that the CanBus communication was "noisy" - or even what "noisy" means in this instance.

If you have added additional modules to your custom vehicle project (BCM, ABS, etc.) then sometimes these interfere with tuning software. Tuning software sends out a "remain in standby mode" command to these additional modules - when attempting to read or write to a PCM, or ECM and TCM combination.

This is not always effective in keeping the other modules off of the communications bus. People who regularly tune OEM vehicles know that certain vehicles require certain modules to be physically disabled (usually by removing a fuse), so that tuning software may be used without issue.

In your case, if adding a resistor on the communications bus made the vehicle "run better" then you have an issue with how the CanBus daisy chain is wired / connected - or you have a mismatch in operating systems and / or module VINs.

[gtstorey]

Mine was using a reworked/rewired wiring harness from a 2009 SS Cobalt with the ECM (w/resistor), BCM and PSCM/EPS that had the second resistor (all from the 09 Cobalt Donor). Basically wired like this but without the TCM http://dfkitcar.com/forum/index.php?...290/post-45351. Everything worked as expected.

When I removed the EPS and replaced it with one without the resistor (Saturn Vue EPS that I could get a controller to adjust the assist), I originally just connected up the 1/4 wires and the 2/5 wires and things went wonky. Adding in the 120 ohm resistor set everything back to communicating like it should. Some of the others that have done this on the DF forum had to add the resistor, some haven't (very small sample size). Pretty much what the aeswave.com link I posted says;

"The network can operate with one open resistor, but the signal will be less stable, and communication errors may occur."

[blindsquirrel]

You have a pre-2009 ECM, and a post-2009 TCM (I found a matching TCM OS ID in a 2017 Silverado, that's possibly also used for 2018). Those are never going to be able to talk to each other, they speak different CAN languages. You need either a post-'09 ECM with your existing TCM, or a pre-'09 TCM with your existing ECM. Service Numbers (the hardware) will need to be compatible with whichever ECM/TCM OS you change to - your early ECM can't be programmed with an '09-up calibration, and your late TCM can't be programmed with an '09-down calibration.

The standalone TCMs are kinda a pain in the ass. And no, you can't convert your current auto trans ECM file into a manual trans file to work with the standalone just by changing the dropdown to 'manual' - that setting does exactly nothing.

[olskool]

Yes, that is correct and now we are learning that will not work. Ok, so I need to correct this so it works the way it should. I was wondering about the stand alone TCM used in the 07 GM trucks with the 6l80E transmission. That sounds like it may not work though. You mentioned the TCM in a 2017 Silverado. So, will that work our current set up/wire harness? Do you have GM part number for the ECM that I should look for? Any information you can provide would be a huge help.

[blindsquirrel]

Nothing from the factory ever used a standalone transmission controller. That's aftermarket/performance stuff.

The 2007 6L80E has the TCM inside the transmission just like the 2017/2018 transmission you have now. But different years use different hardware, so you cannot just reflash the TCM you already have as a 2007.

If you want to keep your existing ECM, then you need a TCM or complete transmission from a 2007 (or, pre-2009). If you want to keep your existing transmission/TCM, then you need an ECM from something made after 2009.

[olskool]

Ok, great to know and thank you. This is what I'm looking at - An ECM for a 2010-2017 GM Express, Caprice, etc... It fits many GM's that used the 6.0L, 6.2L 4.8L etc... Part #1263238. It looks the same as it has 2 plugs like the one we are using now. Then there is another that is used that has 3 plugs - one is BLUE. I assume and believe I don't want that one.

[olskool]

Ok - update on this issue. We purchased a new ECM(E38) and had it VIN programmed for a 2010 or 2011 Express. We were able to write to it, and then...... Same codes are back - no change. Ideas?????

[blindsquirrel]

Ideas? POST THE TUNE FILE.

[relicdew]

Did you pair the ECM and TCM together? Although the 2010+ E38 ECM is required for your setup, you must also get the TCM paired to the ECM.