I’ve used the search function and have checked many possible solutions.
I have a SoS supercharger with AEM infinity. Driving to work and noticed my EPS light was on, speedo tach and coolant gauge were not working. Got the car home and cleaned off the VSS. Now the speedo works, EPS light is off and properly functioning but the tach doesn’t function. I’ve checked the ground behind the cylinder head.
When I plug the infinity into the computer the speedo functions in the app. Anybody have ideas?

 

Plug n Play AEM Inifinty?
Do you have an MIL(check engine light) on the dash?
First thing I would check is to make sure you EPS Control Unit Connector B (14p) is seated properly under the fuse box.
Then make sure the Crank Position sensor is fully seated.
If it's just the gauge cluster, which it sounds like with the ECU reading the tach properly, there may be something wrong with your Gauge Assembly connector below the dash. Wire got cut, pulled, etc. Check to see if anything is loose.

Then check for continuity between Gauge Assembly Connector (20P) pin A5 and ECU connector A (32P) pin A19. If there's not continuity there's an open wire between these two connectors. If that's good, check if there's continuity between the Gauge Assembly Connector pin A5 and a body ground. If there's continuity there, the wire between the gauge assembly and the ecu connector is shorted to ground.

Try that and let me know what you find

 

Often overlooked, make sure the battery is secure in its tray, and that both terminals are seated fully and tight.

 

Yes it’s the SoS plug and play infinity. Everything came out normal. I put it all back together and the tach functions fine. Went to take it for a test drive and I cannot get past 3k rpm and my check engine light is on VERY dimly and fades in and out. The light functions when I put the keys in. My next theory is it’s a ground but honestly I’m lost and have no idea where to go from here.


Edit: Solved. I did the short circuit trick and reset the EPS system with the method mentioned in the helms manual. I’m not 100% what caused the problem originally still but the car runs great.