Circuit Description

WARNING: This page is about a different car, the 2005 Toyota Sienna. However, it is still accessible from the selected car via links, so may be relevant.

The mass air flow meter uses a platinum hot wire. The hot wire mass air flow meter consists of a platinum hot wire, a temperature sensor and a control circuit installed in a plastic housing. The hot wire mass air flow meter works on the principle that the hot wire and temperature sensor located in the intake air bypass of the housing detect any changes in the intake air temperature.

The hot wire is maintained at the set temperature by controlling the current flow through the hot wire. This current flow is then measured as the output voltage of the mass air flow meter.

The circuit is constructed so that the platinum hot wire and temperature sensor provide a bridge circuit, with the power transistor controlled so that the potential of A and B remains equal to maintain the set temperature.

Fig 1: Circuit Description - Mass Or Volume Air Flow Circuit

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 2: DTC Detecting Condition Table

HINT:

After confirming DTC "P0100, P0102 or P0103", use the hand-held tester or the OBD II scan tool to confirm the mass air flow ratio from the "DIAGNOSIS/ENHANCED OBD II/DATA LIST/ALL".

Fig 3: Air Flow Value Table