Section 17 (Engine Controls - Tests W/Codes): Summary
WARNING: This page is about a different car, the 1997 Volvo 960. However, it is still accessible from the selected car via links, so may be relevant.
If no hard fault codes (or only pass codes) are present, driveability symptoms exist or intermittent codes exist, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.