This could be a faulty Body Control Module OR Your engine Immobilisor. The worst thing you could of done is cut the wires to the alarm siren, the computer in your car logs such actions and that's why I am guessing the second time you tried the trick it didnt work.
Is your vehicle remote entry?
Is it a factory fitted alarm or aftermarket?
All the advice I can offer you is this if it is the factory fitted alarm.
1. Lock you vehicle with the remote - Once doors are locked wait 20 secs
2. Unlock your vehicle with the remote
3. Put key in in igntion, and turn to the ON position but do not start the vehicle. wait 15-20 sec and turn it over.
4. if you get nothing, your immobiliser is killing your car
5. If it turns over, leave it running for about 10-15 secs, then turn off, get out and relock the car.
This is the standard reset security code sequence used in cars I have worked on, if that don't work the secondary sequence involves step 2, to change. Unlock your vehicle with the KEY not remote and proceed to so the same steps after step 2.
Lemme know how you go.
**Working PART-TIME for Carjunky for a while, Please bare with me =)**
Going for GOLD in Beijing