No Communication of MS2 After Connection to car

[lesismore]

What I Have: DIYPNP for Bosch 55 pin (1988 325iX) which is MS2/Extra with a daughterboard basically.
Tunerstudio 2.6.14
MS2/Extra FW 3.3.3
The basemap from DIYPNP with engine size and injector size modified (it was set to 2 liters and it's 2.5, and I have bigger injectors)

Basically when the MS is connected to a power supply (just a 12v one I had lying around) it works fine. It communicates to Tunerstudio, I can update firmware, burn new settings to it etc. As soon as I connect it to the cat though it will not connect to tunerstudio. With or without the 12v connection connected it dissapears from the serial port. I at first thought it wasn't receiving 12v from the harness, but even after i connected the power supply I absolutely nothing. To check if it was working (without comms) cranked it and no start. As soon as I plug the old Bosch ECU in it fires right back up. As soon as I unplug the harness it immediately is seen by tunerstudio.

Any ideas? I've gone over [this][/http://www.diyautotune.com/diypnp/apps/ ... 25-mt.html] guide from top to bottom and rechecked all connections from daughter to mainboard.

[Matt Cramer]

Do you have VREF wired to the adapter board?

Are you using the stock TPS?

[lesismore]

Vref: I just have the 12 volts connected to the pin from the 55pin that supply 12 pins (pin 37). I've checked the pinouts of the car (Bentley manual and online) and the pin number is correct. I'll multimeter it later just to check.

TPS: currently the TPS is the stock off/on (any throttle/WOT) sensor. As a result and per the diypnp instructions TPS SIG is wired to ground with a 1k resistor to keep the signal at 0%.

Would either of those fully disable board communication and function though?

[Matt Cramer]

What happens to 12V when tested on the car?