Entering Diagnostic Mode
WARNING: This page is about a different car, the 1997 Lexus SC 400. However, it is still accessible from the selected car via links, so may be relevant.
Turn ignition on, engine off. While holding control switch in SET/COAST or RES/ACC position, press cruise main switch button. After a short pause, CRUISE indicator light should repeatedly flash Code 2 (SET/COAST) or Code 3 (RES/ACC). This indicates diagnostic mode has been entered. Release control switch lever to its normal (neutral) position. Leave ignition on.