technique  
 

Can VOCAL SCW 1 be built into a car driven by a diesel engine?

YES.
Here the detailed explanation:
There are old diesel driven vehicles with a mechanical diesel pump. Thus, for circuit-breaking there is only two electrical circuits available: starter and throttle valve. For stopping the diesel supply a solenoid valve from other antitheft devices and different suppliers can be installed and activated by the third relay.

With later diesel models with EDC diesel injection is blocked using the third relay.