Hello,
Thank you for your question.
Can you confirm that the command has correct structure. There was no such issues when setting this parameter. Make sure that you use double sided dot ':' not space. Firmware version on device is the latest one 03.25.05rev.00?
Example: <Login><password>setparam 2004:98.98.78.78
Information about SMS command on wiki page: https://wiki.teltonika.lt/view/FMB_setparam
There is no such command to stop a vehicle. You can make as an work around putting relay in to fuel pump and connecting with FMB device DIN. Then activating DIN by sms command.
Hope this will help.
Best Regards.