Finally I've managed to find the time to look at this again. I've wired the pump up to a switch red to batt, black to ground. The pump runs. I've put a meter on the pink and its infinite impedance to ground with the pump unpowered, around 30 Ohms when its pumping up. When it reaches pressure the impedance goes open circuit again. The pump ticks slowly but seems really laboured. I haven't tried shorting the pink wire to ground yet to see if its an inhibit/enable line. Is there a diagnostic section for the pump that gives any more info?
Cheers
James

I'll see if I can help.

The harness connector going to the ECM is numbered C51-2. Terminal 18 (C51-2-18) in that connector is the black/orange and goes to the ECM from the 4wd switch. Terminal C51-2-7 is the red wire to the pump from the ECM. Terminal C51-2-27 is the pink wire to the pump from the ECM.  This pink wire is the pressure switch in the 4wd air pump assembly.  You can see the harness connector in the scan3 picture in webshots.

I'll bring my books to work tomorrow to scan some more. I'll also get the dianogstics of the 4wd motor setup.

For a quickie, C51-2-27 pump switch, normal voltage 0-1V, transfer 2H or N, (motor running);
10-14V, 4 seconds after transfer shift lever shifted to 4H or 4L (after motor stops);

Pressure check: 30.0-45.o kPa (4.25-6.4psi).
Pump motor should stop after 10 seconds, ECM turns off the motor after 10 seconds to prevent motor damage. So it looks like if you setup a pressure switch in the 45kPa range, you should be good to go. Now to place it somplace? Maybe in-line with the feeder line to the diff?

Thanks again, I plumbed the pump in properly tonight and tried it again. I think I must have had a little bit of a leak the last time I tried it cos it seems to work just fine now (all new pipe). It runs for a few seconds until the pressure builds up and then stops. Every 10 secs or so it runs for another couple of clicks to top it up. When I turn the switch off there is a very audible release of pressure. I'm wheeling this w/e so I'll let you know how I get on.