Section 20 (Engine Controls - Self-Diagnostics): Summary
WARNING: This page is about a different car, the 2002 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
If no diagnostic trouble codes are present, but driveability symptoms or intermittents exist, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent procedures.