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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.
Test 1: Engine running. A counter accumulates the time during which the mass air flow has exceeded 10 g/s. Counter has reached 400 s.
Test 2: Engine running. A substitute value is calculated for the engine coolant temperature: The starting intake air temperature is incremented with 1C per 60 g air mass/s. A counter accumulates the time during which the air mass flow has exceeded 10 mg/s. A maximum is set for the substitute value after 350 s that is dependent on the intake air temperature (normally 65 -80C). The maximum value is set as soon as the air mass/combustion is not too high and the air mass/s is not too low, so that the intake air temperature will be as close as possible to the outdoor temperature. After 400 s, the sensor value will be compared with the substitute value.