Saxo immobiliser issue

[flexinoodle]

The Saxo was off the road for 12 months, battery went dead, usual scenario, however, having done as much reading as i can, i seem to have a different issue to most.
Charge in battery
Red light flashing on keypad as normal
Type in code, red and green light (Wrong code, but its the right code)
Tried the factory codes (Didn't expect these to work) 0000/0001/1111
Turn off the ignition and goes back to red light
Buttons are all beeping when pressed, and the fact that the red and green comes on after code and not when ignition engaged, definitely suggest ECU is not faulty
But it seems that the ECU has forgotten the code entirely ?
Has anybody come across this before ?

[xantia_v6]

Red and green lights together may indicate that the keypad is not communicating with the ECU, maybe because the ECU has lost one of its power feeds (blown fuse, corroded connector or broken wire)

[flexinoodle]

No, the red and green only happens after entering a code, this is the fault for wrong code, if its an ecu wiring issue, the green and red stay lit apparently