Enable criteria

• The following conditions should be fulfilled within 5 sec. to be able to start the diagnosis: Coolant Temperature and inlet air temperature when starting exceeding +40 °C and the difference between coolant temperature and inlet air temperature greater than 5 °C.

Idling speed. Max. one change of status of the brake light switch. Purging adaptation higher than -6%. Tank pressure between -300 and +100 Pa. Inlet air pressure at least 20 kPa lower than the atmospheric pressure. The vehicle stationery. The volume of fuel in the tank 9 -54 litres. Battery voltage between 10 -16 Volts. Tank pressure sensor diagnosis should report OK.

When the above condition is fulfilled for more than 5 sec. the diagnosis will start. The diagnosis will be interrupted if the purging adaptation exceeds -8%. Should the diagnosis be interrupted the speed must exceed 0 at one stage before the diagnosis is allowed to be restarted. The diagnosis is divided into three phases, A-C:

Phase A) Evaporation check  The shut-off valve is activated (closed) at the same time as any purging is interrupted for 4.5 sec. The tank pressure is observed, decreasing pressure reveals a leaking canister purge valve. Increasing pressure by more than 4 Pa/s hints at fuel evaporation, in these cases Phase A should be repeated. If it then continues to rise by more than 4 Pa/s quit the diagnosis. To be able to continue, vehicle speed is required for a short time. When the pressure increases less then 4 Pa/s Phase A is complete. The diagnosis continues to Phase B (pressure decrease)

Phase B) Pressure decrease  Shut-off valve is still closed, canister purge valve pulse ratio is set to 18% until the tank pressure has reached -600 Pa. This decrease in pressure should take Max. 30 sec.

Phase C) Maintaining pressure  The shut-off valve is still closed, canister purge valve is closed. The tank pressure is observed for max. 12 sec.