Think City with Gen 1 PCU have a very strange and hard to find connector.
The connector is hanging freely above the passenger foot well.
I replace these with another connector that is usually used on a cars with Gen 2 PCU.
pin 1 - Black/Green
pin 2 - Green/White
pin 3 - White
pin 4 - Grey/Black
| SIADIS | PCU | RS232 | Signal |
|---|---|---|---|
| 1 | 6/62 | 2 | TX |
| 2 | 5/62 | 3 | RX |
| 3 | 4/62 | 7 | DWNLD |
| 4 | 3/62 | 5 | GND |
Pinout of the ftdi adapter for using with usb.
http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_Chipi-X.pdf
Here are couple of photos showing the result and pinout.

