as I said - there are some type of car robbers that have tow trucks and come along bars to pull the car too, no immobiliser can stop that.
A very simple car thief detterent system Ive seen in action was an industrial type 12V relay. to cut off main power to the starter motor and also a small relay in the starter solenoid circuit - firstly the thief cannot try to hotwire it as the main cable has zero volts in it, shorting with a screwdriver wont work as the wire
from the battery to the starter needs to be thick.
this was a BMW E36 318i Automatic - the car also had a system that blocked the crank sensor, cam sensor and fuel pump control lines individually, all this enforced that the assumptive car robber would need to spend some good time with the ECU wiring, starter lockout wiring, and transmission lockout wiring to start the car.
