Corsa 1.2 16V , immobiliser activated . Need help ...

[D1546]

Hello ,
I have a problem with my corsa 1.2 16 V 1999 . I've bought the car about 2 weeks ago and everything was ok until yesterday when tried to start the car and it won't start .
The EML flashes about 3 times and I can hear a click under the bonnet when I try to start , the engine turns but won't fire. The fuel pump it's ok ( i have connected it directly to the battery and it is fine ) and the fuel pump relay is ok too ( same checked it directly to the battery and it clicks) , so the only problem has to be the immobiliser.
What can I do now ? how to deactivate this ? Do I have to reset the ECU , will it help? how to do it?
Any advice would be appreciated as I am stuck with the car unable to go anywhere .
Thank you ,

[Octane2097]

If it is the imob it Could be the transponder in your key, have you dropped your keys or got them wet lately?
If you have a spare key try that one, if not you will need to get a vauxhall specialist to ether deactivate the imob or get a new key.

[D1546]

Thanx for reply,
No , I haven't dropped the key or got it wet and I have only one key .
What I did though was to install in a second hand radio , as I bought the car without one ( and some say this might have activated the immo) . Anyway if I disconnect the radio still the same problem . I've tried disconnecting the battery for 1 hour ,too, but no luck ...
I was wondering if I'll take it to a garage to reset the ECU will solve the problem ? (this garage is about 1 mile from where I live so I could tow the car there , otherwise the closest dealer is 35 miles away and taking the car there would be more complicated)

[LSKSK]

Second hand ecu transponder and keys?
I just bought 2 ecu's for £20

[corsa beast]

dont know if its related but i had a problem with my immoboliser when my battery in the fob was getting low..had to put on and deactivate it twice before i could start the car up