Fault Criteria: Notes

WARNING: This page is about a different car, the 2003 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

The diagnosis was improved on M97 and has now been further improved to prevent the Check Engine lamp from going on when there is no fault. The major revision on M98 is that the diagnosis is performed twice during the same driving cycle, if the coolant temperature is below 40°C (104°F) when the engine is started. Both the cold start diagnosis and the regular diagnosis must be performed and a leak indicated during both diagnoses, before a DTC is generated.

The diagnosis is performed once each trip and is used to determine whether there is a leak corresponding to a hole of diameter 1 mm (0,040") in the evaporative emission system.

The system includes a tank pressure sensor and a shut-off valve for the air supply to the EVAP canister.

When the conditions for the diagnosis have been fulfilled and the air supply to the EVAP canister has been stopped, the tank pressure will be controlled by the EVAP canister purge valve.

The diagnosis starts by storing the value from the tank pressure sensor.

Then, the PWM ratio of the purge valve is set to 15% and the EVAP shut-off valve closes. The purge is interrupted when the tank pressure has dropped by 0.6 kPa.

The rate at which the tank pressure increases is now monitored.

The fault criteria are fulfilled if a pressure drop of 0.6 kPa cannot be achieved within 23 seconds, or if the tank pressure increases more than 0.3 kPa during 9 seconds after the purge has been interrupted.