2005 Toyota Avalon FOB stopped working, have a replacement. Now believe accidentally deactivated vehicle's ECU by turning ignition on/off 5 times during process of adding new FOB. So now, how can I get receiver in car to accept signal codes from remote? It is not a smart key system!
Not enough information to make sure I am answering the question. Why do you believe that the ECU has been deactivated? Does the car not start?
Not sure of the procedure that your used, but take a look at these instructions and try to reprogram the remote.
Remove the key from the ignition. Lock all of the doors, but open the driver’s side door. Leave it unlocked. Insert the key into the ignition twice within five seconds. Don’t turn it. Close then open the door twice. Insert the key again then remove it from the ignition.
Close then open the driver’s side door. Close then open the driver’s side door again. Insert the key. Leave it in the ignition. Close the door. Turn the key to “On,” without starting the engine, and then turn it off. Remove the key. You’ll hear the door locks sound.
Push and hold “Lock” and “Unlock” buttons on the remote for two seconds, and then release the buttons. Then push and hold “Lock” for three seconds. The remote is now programmed.
After this the remote should work after this. If the car would not start before, try it after locking the car with the remote, unlocking it and then open the drivers door put the key in and try to start it.
Again, not sure I'm answering this correctly based on your short description. If not, try to clarify the issue and we'll see if there is a better answer.