Circuit Description
Hot wire mass air flow meter consists of a platinum hot wire, temperature sensor and control circuit installed in a plastic housing. Hot wire mass air flow meter works on the principle that hot wire and intake air temperature sensor, located in intake air by-pass of housing, detect any changes in intake air temperature. Hot wire is maintained at set temperature by controlling current flow through hot wire. This current flow is then measured as output voltage of mass air flow meter. Circuit is constructed so that platinum hot wire and temperature sensor provide a bridge circuit with power transistor controlled so that potential of A and B remains equal to maintain set temperature. See Fig 1. If DTCs P0100 or P0102 are set, there is an open or short in mass air flow meter circuit for more than 3 seconds. If DTC P0103 is set, there is an open in mass air flow meter circuit for more than 3 seconds (E2G circuit) or short in mass air flow meter circuit for more than 3 seconds (+B circuit).