Assuming its the cylindrical hot film AFM rather than the flap type, the wires are; earth, 12v feed, 5v reference feed and the sensor return signal. I can't remember which pin is which off hand. I'll have a look at my notes in the garage tomorrow and post another reply.
On the other hand, do you have access to a multimeter? If so you'll easily find the earth, 12v feed, etc. by hooking up the AFM and probing the back of the connector with the probes.