I neeed help PLEASE fellow Ford lovers, I have a 2004 BA XR8 Falcon 5 speed manual.
Recently a "Security Code Error" is coming up on the display and the car won't start.
It has been to multiple workshops, they have replaced the ECU twice, and I still getting the same error andcthe car won't start.
I have replaced the battery and the keys reprogrammed.
I have sent over 6k trying to get this issue sorted.
PLEASE HELP, I'll try anything to fixed this.

they have replaced the PCM or the BEM?. when you say "won't start" what exactly do you mean?. how did you get the keys reprogrammed? coz whilst the code error is up i don't believe it will accept key reprogramming. is there any problem with your ignition switch? also has your ICC been replaced/removed at any stage?.

Thank you for you reply, when I said it won't start. The dash lights up like it would be you turn the car over, than nothing.
A red warning display light comes on, I checked the service book and it is the engine immobilizer symbol.
They said they replaced the ECU (computer) twice.
I have had RACQ & NRMA put the scan tool on it, both time they said there is no fault code.
The mobile Auto locksmith said there is nothing wrong with the keys.
When it happened last week, I tried a Utube hack, by holding the menu and AM button down together for 10 seconds and it worked.
However it doesn't work anymore.
When the car is running it goes really really well.

what's highlighted normally is done when replacing the ICC .... so it 'appears' you have a problem with the ICC/BEM. i believe you need to join {DESCRIPTION} so you can get more detailed information re your car's problem. and that's about the best i can do to help you.

Thank you for your assistance, I joined FordForum yesterday.

hopefully all is answered there. good luck