- Start the car and let it warm up until the radiator cooling fan has come on twice.

Leave as little time as possible before starting the test once the engine is warm and avoid leaving the engine to idle for long periods.

Check that the probe diameter is at least 0.22 times the diameter of the exhaust pipe.

Ensure that the exhaust gas intake fittings do not allow leaks.

- Position the fume meter measurement probe in the end of the exhaust pipe, ensuring that its end is positioned in a pipe section where the gas flow is evenly distributed.

- If necessary, to meet the above requirements, apply an extension to the exhaust pipe so that the coupling to the exhaust pipe is sealed and the end of the probe is positioned in a long straight section towards the engine that is at least six times the tailpipe diameter and at least three times the tailpipe diameter downstream.

Check that the probe intake pipe from the tailpipe to the fume meter is on an ascending gradient without any sharply angled joints.

Ensure the counterpressure at the probe is as specified and does not exceed 7.5 mbar during the test.

- With the engine running at idle speed, place the gearbox in neutral and release the clutch pedal.

- Position the fume meter so that exhaust gas can be drawn off.

- Take the reading shown by the fume meter pointer.

- As the engine is idling, operate the accelerator pedal quickly but smoothly until the engine is running at maximum rpm and the regulator cuts in.

- Record and note down the maximum fume level indicated by the fume meter during acceleration without taking values during the release stage into account.

- Once the maximum rotation speed has been achieved, release the accelerator control until the engine resumes idling.

- Check that the fume meter pointer returns to the position measured previously at idle speed.

- Repeat the above operations at least six times until the fume readings stabilise.

The readings may be considered stable when they are within a band that is 1.25 m-1 wide for four consecutive readings and not in decreasing order.

- The fume value to be considered is the arithmetic mean of the four stabilised values.

- Check that the fume level meets the required value stamped on the vehicle marking summary plate located in the engine compartment and indicated in the following table.