ECU issues

[deesvtsT]

I changed my front wireing loom from a s reg into a r reg vts because of a broken wire to my rev counter,it all works fine so i changed the ecu and transponder ring round the barrel and the key
as my old ecu had a idle problem but now the key light is flashing and it wont start if i put the old back on and it runs thay are both single plug ecus and have the same numbers on is there something i have missed or not chang:wall:ed

[mcjacko1987]

does ur old ecu start the car? if it does put it back in.
sounds like the immobiliser is locking it.
put ur old ecu in. turn the key so engine starts up, remove the immobiliser box. you will find this very well hidden up behind the glove box, look under the dash and reach right up. you will find a box about the size of a pack of 20 fags looks like this:
http://i1101.photobucket.com/albums/g432/mcjacko1987/DSCF0394.jpg
http://i1101.photobucket.com/albums/g432/mcjacko1987/DSCF0395.jpg
with the engine running remove this box. turn off ignition. then see if the car starts up again. if it does its ready to use another ecu.
however with you putting your new ecu in with the immobiliser in the immobiliser will now have locked the new ecu so you will have to pay to get it unlocked (around £40 a few people do it on here). then you can plug that ecu in and the other ignition barrel and all should be fine :y:

[adamspencer]

did you swap the immobiliser from the doner aswell? Cos each ecu is paired with a single immobiliser: if its wired into a different one, it'll refuse to work altogether