E38 with T42 and 4L80E swap - ABS light C0055

[adunphy]

Support suggested I post here to see if any tuners have a suggestion or have run into this. The engineer reports the code is working fine so it "must be in the tune"

I have posted over on PerformanceTrucks.net the detailed issue along with screenshots and all the PD I've done so I'll try to make it breif here.
see details here: https://www.performancetrucks.net/fo...tom-5a-549072/

Its an 07 NNBS Silverado with 4L80E swap. I used the 08 Express van TCM and repinned my harness, added the ISS, and moved the wire at pin 45 to pin 26 at the TCM. Everything functions perfectly and has for the last year +.
ECM: 1250212
TCM: 24239927
MAF_only_CL_v1.9.abs.hpt

There is a nagging issue when doing a moderate-hard launch and the converter flashes up to stall speed and after a few seconds I get the ABS light on solid (no brake light). If I scan the EBCM I get the C0055 with symptom code 5A which is a "Not plausible".

If I reproduce the problem while scanning the EBCM and watch the rear wheel speed signal it stays at 0mph until I get out of the pedal and then it comes back. That short period of 0 speed is enough to throw the ABS code. During this time my speedo works fine and the OSS is reading like a champ (I confirmed with a fluke). I am also able to reproduce the issue in reverse. If I'm rolling at any speed over 0mph and nail the throttle, there is no issue whatsoever, its only from a dig.

As best i can tell, the Truck EBCM is different from the express van EBCM and possibly the reason code I'm getting is not part of the VAN EBCM's code? It seems like the TCM is doing some sort of slip diag and leaving the rear wheel speed signal to the EBCM flat at 0 until its done. HPTuners was not able to definitively confirm this theory and reported the code is fine so I figured I'd ask here. Its such a drag to see that light come on with everything else working perfectly. Any help from anyone who may have seen this before is appreciated.

[adunphy]

Bump... Nobody has seen this? I was hoping that since so many people have done the 4L80E swap on these trucks with the 08 Express VAN TCM this would be common but I guess not?

Any help or advise would be appreciated. I've been chasing this issue for over a year now and would love to at least figure out the cause.

[mbray01]

have you considered that when accelerate going forward the truck lifting to one side, and dropping on the other may be "flexing" the cable. it may not do it in reverse as its twisting the opposite direction.
just another thing to cosider

[adunphy]

Thanks for the suggestion. I did try the reverse test early on and I can produce the same exact results in reverse. I have also run overlay circuits for every speed sensor related wire I can find (according to the GM repair manuals) but still see the same exact behavior. While it sounds like a mechanical problem it really acts more like a programmatic one but I am still 50/50 on whether its code related or mechanical at this point. In another forum someone pointed out that the C0055 is not a valid code on the 08 Express van EBCM module. Since the Express van EBCM is a completely different from the NNBS Silverado harness and pin-out, I cant swap out to one to test the theory.

[WS6HUMMER]

Thanks for the suggestion. I did try the reverse test early on and I can produce the same exact results in reverse. I have also run overlay circuits for every speed sensor related wire I can find (according to the GM repair manuals) but still see the same exact behavior. While it sounds like a mechanical problem it really acts more like a programmatic one but I am still 50/50 on whether its code related or mechanical at this point. In another forum someone pointed out that the C0055 is not a valid code on the 08 Express van EBCM module. Since the Express van EBCM is a completely different from the NNBS Silverado harness and pin-out, I cant swap out to one to test the theory.

Sorry to raise this one from the dead but did you ever figure this one out? My daily is a 2008 1500 with a 4L80 swap & a 3200 stall circle D converter and anytime I get on it I get an ABS light a C0055 & a blinking CEL like a miss but no misfire code. I've been ignoring it but it happened again this morning and now I'm curious as to why.

[adunphy]

In the end, I determined that it was an OS compatibility issue between the 2007 Silverado (E38) ECU and 2008 Express Van (T42) TCM that couldn't be resolved without using the OS from the 2008 ECU that was paired with that TCM originally. No matter what I tried I couldn't get past it so just lived with it.

I've since sold the truck but if I had to do it again, I might try loading the 2008 Express van ECU OS and tuning from there. When I looked at the 2008 calibration I did see some minor differences in the Speedo cals and I suspect that is where the gremlins resided. Good luck!

[WS6HUMMER]

In the end, I determined that it was an OS compatibility issue between the 2007 Silverado (E38) ECU and 2008 Express Van (T42) TCM that couldn't be resolved without using the OS from the 2008 ECU that was paired with that TCM originally. No matter what I tried I couldn't get past it so just lived with it.

I've since sold the truck but if I had to do it again, I might try loading the 2008 Express van ECU OS and tuning from there. When I looked at the 2008 calibration I did see some minor differences in the Speedo cals and I suspect that is where the gremlins resided. Good luck!

Thanks for getting back with me, when I did my swap I was told HPT couldn't do the swap at the time. I had Frost do the swap with EFI live but I couldn't tell you what file he used or exactly what he did. I've since done the swap for other people via HPT with the sloppy mechanics write up and the express file from the repository. Looks like I'll be living with the issue too.