[guye]

Andy, I know your vss signal works for your speedo, but when you tried hooking it up to the ECU, did you disconnect the speedo?

And did you try swapping the pins as Ben and others suggested?

Failing that, another option is to use the brake light - wire that direct to the lockout solenoid (via a relay) bypassing the ECU altogether. So you can only select reverse while your foot is in the brake.

But getting speed to the ECU is better. If you want to use things like Harry's Laptimer or Dashcommand, or just service computer read, off the OBD2 port you'll be missing heaps of info. Not to mention the diagnostics will be reduced - distance since last reset, fuel consumption stats, etc (I know, I know, who cares about fuel consumption - but you get what I mean...).