Circuit Description
Mass air flow meter uses a platinum hot wire. Hot wire air flow meter consists of a platinum hot wire, temperature sensor and a control circuit installed in a plastic housing. Hot wire air flow meter works on principle that hot wire and temperature sensor 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 air flow meter. Circuit is constructed for platinum hot wire and temperature sensor to provide a bridge circuit with power transistor, and controlled for potential of "A" and "B" to remain equal to maintain set temperature. See Fig 1.
DTC P0100 is set when ECM detects an open or short circuit for more than 3 seconds, with engine speed about 4000 RPM. DTC P0102 is set when there is an open in mass air flow meter circuit for more than 3 seconds with engine speed at 4000 RPM or less. P0103 is set when there is an open in mass air flow meter circuit EVG for more than 3 seconds. P0103 is set when there is an open in mass air flow meter circuit +B for more than 3 seconds. Possible causes are:
- Open or short in MAF circuit.
- Faulty MAF sensor.
- Faulty ECM.