E39 stand-alone VSS stuck at 158mph

[TurboWood]

Hi,
I'm trying to resolve a long standing issue with my setup --> VSS stuck at 158mph. I see a lot of mention of this with swaps using the E38 PCM, but I'm not sure I have the right solution. Lots of posts talk about changing the PCM, while others talk about needing a TCM to provide a CAN signal.

Basic info on my setup:
- E39 out of a 2011 Regal (VIN: 2G4G15GVXB9164001)
- No BCM or TCM
- LDK engine
- VSS (GM p/n 55568130) mounted to see reluctor wheel on rear axle (I know this is a transmission speed sensor)
- VSS connector (vehicle side) pinout attached

What I understand about E39 VSS:
- There was a change in wiring in the middle of 2011 model year which moved "VSS High" and "VSS Low" signals in the PCM
- VSS High = +5v --> for my PCM I'm pulling from pin 5 of J2
- VSS Low = ground --> for my PCM I'm pulling from pin 21 of J2
- Voltage measured at sensor across VSS high and VSS low is confirmed to be +5v
- VSS signal is pin 8 of J2

Questions:
- In the 2011 and later Regal where does the wire from Pin 8 of J2 go (VSS sensor or TCM/BCM)?
- Is the PCM expecting a CAN signal to Pin 8?
- If the PCM is expecting a VSS sensor input, is there a different sensor I should use?

Thanks,
Daniel

[tunerpro]

You don't say if the calibration you are working with is originally from an automatic or manual transmission equipped vehicle. If it was originally an automatic, then you are not getting a VSS signal because the ECM is expecting to receive a message from the TCM (which doesn't exist) describing how fast the transmission output shaft is rotating. The only way to fix this is to either find a manual transmission OE flash in the repository or us the GM tools to flash it with a manual transmission VIN.

If it was a manual transmission vehicle, then it's probably a wiring issue.

[TurboWood]

Thanks for the quick feedback. I don't have any idea what transmission the vehicle had. I tried searching by the vin, but the transmission didn?t show. That said, based on what you are saying I bet it was auto.

Do you know if it is indeed pin8 that would receive the TCM signal or it connects somewhere else?

*edit

I believe I confirmed it was an automatic and as best I can tell the CAN lines are J1 pin39 and pin40. I assume the TCM would have been connected to the CAN bus and communicated over those pins. Those should also be going to the OBDII port so maybe there is a way to send a signal from there, but that's not ideal.

So, does anyone know of a way to send a speed signal over CAN?

@tunerpro: what "respository" are you talking about? Would I still need the GM tool?

Daniel

[tunerpro]

That VIN is indeed from an automatic transmission (go to https://tis2web.service.gm.com, type in your VIN, and select TCM - you will find OE calibration info).

Unfortunately unless you know how to correctly form the TCM message that reports the speed signal, including the bit conversion, meaning of the data, and all rolling counters and integrity checks, you won't be able to just add it through the CAN bus.

Your best bet is to find a manual transmission calibration file, flash your ECM with it, and wire up the speed sensor to the ECM. Good luck!

[TurboWood]

With some help from zzperformance I was able to flash a factory manual tune onto the ECM which has at least resulted in speed reading zero! I still don?t know for sure if the sensor reads properly or not, but I think this is still a step forward. I?m also relatively confident that I have the right pin out for the sensor so hopefully it?s just a question of having the right trigger wheel.

Thanks again for the help.

Daniel