Diagnostic Aids
WARNING: This page is about a different car, the 2003 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.
DTC is set when heater operates, and heater current exceeds 2.35 amps (2 trip detection logic), or when heater operates, heater current is 0.2 amps or less (2 trip detection logic).