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WARNING: This page is about a different car, the 2001 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

General condition for this diagnostic trouble code: Atmospheric pressure must exceed 72 kPa as well as coolant and intake air temperature must exceed -7°C.
Main relay voltage exceeds 10V. Speed above 45 km/h for longer than 60 s accumulated time. Coolant temperature between 78 and 115 °C. Engine speed between 700 and 4000 RPM. Purge active. No fuel shut - off. No change in bypass valve status. Pressure ratio for pressure after and before the throttle between 0.2 and 0.7. Throttle opening between 50 and 500 mm 2. Even engine load.
Mass air flow is calculated using the throttle valve angle and pressure difference before and after the throttle.