DTC P1231: Throttle Position Sensor 1 and 2 Circuit. Sum Out of Range (No Limp Home).: Procedure
WARNING: This page is about a different car, the 2003 Saab 9-3 and 2002 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.
Discuss with the customer how often and how long the symptom has appeared and if it requires replacement of the throttle body.