Fault Criteria, Fuel Evaporation M96 1/2

Diagnosis is carried out once per trip and its purpose is to determine whether leakage in the fuel evaporation system occurs which is greater than would be caused by a hole with a diameter of 0.040".

Included in the system are a tank pressure sensor and a shut-of valve for supply air to the evaporative emission canister.

When the conditions for diagnosis are fulfilled and the supply air for the evaporative emission canister is shut off, the purge valve should be able to control the tank pressure.

Diagnosis starts by the tank pressure sensor value being stored.
The shut-of valve for the evaporative emission canister is then closed.
Purging is stopped when the tank pressure has dropped by 0.4 kPa.
The speed with which the tank pressure rises is now observed.

The fault criteria are satisfied if a pressure drop of 0.4 kPa cannot be obtained within 10 seconds or if tank pressure rises too quickly in 10 seconds from the time purging was stopped.

Conditions For Diagnosis
^ Diagnosis not yet performed this trip
^ Transition diagnosis of front heated oxygen sensor OK
^ Vehicle speed = 0 for 7 sec.
^ Idling speed
^ Purge valve active
^ Additional fuel from purging <10 of engine's fuel requirement.