Do they work on diesel vehicles?

They do not work on diesels vehicles.

Exhaust Controllers only work on petrol cars with valved exhaust systems for sound control.

Note: Exhaust Controllers can only be installed on valves that are specifically used for sound control as part of the muffler system. Please do not install an Exhaust Controller on the single valve located in the middle of the exhaust system. This is not for sound control and should not be interfered with.