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.