RS232 Cable Instructions

Solder the white 4 pin header into spots 1-4 on your ECU in the spot labeled CN2.  The cable is already pinned correctly but here is the pinout.
This is how you connect the cable to your ECU.  It is pinned correctly as is.
Serial Adapter
       ECU SIDE
RS232 -->TTL
       CN2 plug
          Brown = Ground
      PIN 1 (GND)
          Yellow = Receive
      PIN 2 (TX)
          Red = +5 volts
      PIN 3 (+5v)
          Orange = Transmit
      PIN 4 (RX)
      PIN 5 NOT USED
Nick of ECUControl has a good write-up as well. Please refer to it if you need further assistance.