'92 Disco immobiliser probs?

'92 disco 3.5 v8EFI (petrol )
The disco was running fine 'till one morning when the doors would not open. Opened door using the key, car would not start. Called AA who managed to start it by shorting the starter motor. I was told that it was "an immobiliser fault" and was told how to by-pass it by putting in a push-button starter wired directly from the battery via switch to solenoid. Tried this and it still won't start. I checked and found that power was getting from the battery to the connector that was to go on the solenoid (so that works). Any ideas .

Is the immobilser factory fitted or aftermarket?

Corin
Immobiloiser is factory fit.

I have a 96 Disco and had the same problem but my was a 300TDI, It can be embarrassing at times..
What I did I opened the immobilizer to inspect the circuit board and found that there was cracked soldering on the main power relay , fix the soldering and it work fine..
You can also just jumber the main power relay contact and ploblem solve just you won't have a functioning immobilizer.
Cheers

Despot

Hows the battery in the fob? If its armed with the fob it must be disarmed with the fob unlocking it with the key after arming with the fob wont work
I think lol,can you get in test mode or sync mode is the led doing anything ?

hihad same prob with mine changed the imoberliser nothing
so started rewiring stuff to then reed a thred
about a simlar pro all my probs doors wouldent open elec windows
same
the course was there are three fuseable links on drivers side
iner wing taped in side of a cloth typr materal
cut this away there is two wires from batt that go"s into four
then in to three that go into wiring loom
mine where coroded but conected
but had gone green and not doing there job pulled them apart
and put them on a fuse box
hope this helps
thanks martin