Rich,
My understanding of the coded stop solenoid is that it cannot be bypassed by wiring into the 4 or 5 pins, as they only accept digital signals. The only way out is to butcher the protective shield and connect and ignition live to the stop solenoid. This is probably easier and safer with the pump removed
However, a quick google turned this up on Preloved.co.uk:
"The procedure i took works for diesel, pre hdi. First of all I disconnected the battery.To the side of the pump is what appears to be a black case with 4 wires entering it, working gentley with a screwdriver i removed the end cap which revealled some epoxy resin, this is only about 1/4" thick, tap it quite firmly and it will break, underneath is a small circuit board covered in some kind of jelly, this jelly will rub off with your finger, Just so you understand the positioning lets say where the four wires are soldered to the circuit board is at the bottom. At the very top is a soldered joint, desolder this joint and the circuit board will come away, and that spells the end to your immobilizer problems because the connection you have just desoldered is the wire going through to the fuel shut off solenoid, run a 12v supply to this connection via a fused connection and your away be sure to feed the solenoid from a circuit which is live only when the ignition is turned on or you'll never turn the damn thing off. I hope this has been of some use to you all...WIPPPEEEEE NO MORE KEYPAD........ "
Can't comment on its efficacy or otherwise obviously, but it's got to be worth a try before having to remove the injection pump....
