Circuit Description
WARNING: This page is about a different car, the 2003 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.
MAF sensor uses a platinum hot wire maintained at a constant temperature. Airflow past sensor affects temperature and current flow through sensor. DTC P0101 is set when throttle valve is fully closed, MAF sensor output is more than 2.2 volts, and THW is greater than 157°F (70°C).
DTC P0101 will also set when VTA output is .1 volt or more, and MAF sensor output is less than .4 volt for 6 seconds or more at engine speed of zero RPM or more. Possible cause is a faulty MAF sensor.