Here's the background, I've upgraded to the 4l80e from a 4l60e and instead of using a conversion harness and have the PCM control the transmission I purchased the TCI EZ-TCU. I have the VSS signal going to the TCU then using the TCU 4000ppm output signal and Dakota Digital SGI-5 to convert signal back to usable signal for the PCM VSS input. So now with the correct calibration ratio I am reading correct speed on speedometer and HPtuners VCM scanner. now my questions portrays to how I should setup the PCM in HPtuners to use with the TCU properly. Currently I have the automatic tune set to a manual transmission with all the auto trans codes turned off. I've adjusted the idle RPM and rolling RPM a bit but don't think the in-gear selections on those settings are working, maybe this is because I have it set to manual? So the issues I'm currently having is with idle sometimes being unstable when I put it into gear if I idle too long in park or neutral. Also another side thing is that my cruise control is not working? could this be because I don't have a clutch switch and the tune is set to a manual? Anyways just looking for the best way to set up this tune. Thanks.

 

The best way would have been with the factory pcm controlling both. You have to run the tune as manual since the pcm isnt seeing the transmission. Having the VSS signal hooked up will help alot but it still wont ever know what gear your in.

 

Well yeah I know best would have been with factory PCM, but I want paddle shifters Also having TCC and economy switches on my dash is really nice. I also have to abide by commiefornian emissions so I wasn't able to find any information on flashing the PCM to a truck PCM would pass. But I guess you confirmed that the PCM doesn't acquire gear selection signal from the switch on the shifter itself?

 

Cpt.,

Can you elaborate on how and why you have to use the Dakota box to send VSS info to the LS PCM? My engine swap car will have a 4L80E using the EZ-TCU and factory LS PCM and I though I could just piggyback the GM PCM VSS input onto the rear VSS wiring the EZ-TCU is connected to. Any info you could provide would be greatly appreciated!

S.F.

 

I thought I'd be able to do the same but having both the PCM and TCU connected directly to the VSS sensor causes the signal to be destroyed. I found out during testing that both device has an electrical load effectively destroying the signal to each unit. The DD SGI-5e is able to convert the square wave signal from the speedo output of the TCU and convert it back to the sinewave signal that is produced from the VSS sensor. Note you only need to connect the VSS high signal, VSS low is only used for a sensor ground. Let me know if you have anymore questions.

 

Excellent, thank you for clarifying. Just saved me a ton of time figuring out that piggybacking the VSS signal wouldn't work.

S.F.