Circuit Description
Mass airflow meter uses a platinum hot wire. Hot wire mass airflow meter consists of a platinum hot wire, a thermistor and a control circuit installed in a plastic housing. Hot wire mass airflow meter works on principle that hot wire and thermistor located in intake air bypass 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 airflow meter. Circuit is constructed so that platinum hot wire and thermistor provide a bridge circuit with power transistor controlled so that potential of "A" and "B" remains equal to maintain set temperature. DTC P0100 is set when an open or short is detected in mass airflow meter circuit for more than 3 seconds at engine speed of 4000 RPM or less. DTC P0102 is set when an open or short is detected in mass airflow meter circuit for more than 3 seconds at engine speed of 4000 RPM or less. DTC P0103 is set when an open in mass air flow meter circuit is detected for more than 3 seconds (E2G circuit) with engine speed of 4000 RPM or less or a short is detected in mass airflow meter circuit for more than 3 seconds (+B circuit) with engine speed at 4000 RPM or less. See Fig 1. Possible causes are:
- MAF meter circuit is open or shorted.
- Defective MAF meter.
- Defective ECM.