The recommended frequency: each 50 000 km of a run or 24 months.
You make check of system of production of the fulfilled gases in several hours after switching off of the engine.
For free access to system of production of the fulfilled gases lift the car on the elevator.
Check pipes and their connections for lack of leak of exhaust gases which demonstrate their serious corrosion or damages.
Check a condition of arms and suspension brackets of system of release.
At the same time examine the car bottom on lack of through openings, corrosion, open seams, etc. through which the fulfilled gases can get to interior of the car. Cover with silicone sealant all found openings.
Check that elements of system of production of the fulfilled gases were established freely, without tension, with a sufficient gap concerning body elements.
Check a condition of the engine, examining an internal part of an exhaust pipe. If the pipe black is also covered with a layer of soot or white flakes, so the engine needs to be adjusted, including full survey of fuel system.