Fuel/trip computer problem

[ValverRob]

For some reason my fuel computer has stopped giving me mpg readings, its stuck on gal/h, all I can think is that it doesn't know the car is moving, so, where does it get the signal to say its moving? is it from the abs sensors or that little electric box of tricks on the back of the speedo? (its a cable drive speedo)

Also, where is the air temp sensor plug? is it on the passenger side of the bulk head? I put the trip computer in myself and all the wiring was already in but I didn't get the air temp sensor, although another idea I had was to connect it to the intake air temp sensor (or add another one) for when I put the turbo on, would that work? I already know if its hot or cold outside so I'm not too bothered about the air temp sensor!

Thanks
Rob