Use the
isEngineOn command.
First give the vehicle a name, for instance
OneCarefulOwner, then
Method 1 - TriggerPlace a trigger, dimensions 0 x 0, activated Once and make the condition
isEngineOn OneCarefulOwner
and launch your script in the On Activation line.
Method 2 - Waiting scriptAlternatively, if the script is already running and you are just waiting for the engine to start, use the line
@isEngineOn OneCarefulOwner
and the script will continue.