Description

DATA TROUBLE CODE: P0100

SYSTEM: Mass Air Flow Circuit








CIRCUIT DESCRIPTION
The Mass Air Flow Meter uses a platinum hot wire. The hot wire air flow meter consists of a platinum hot wire, thermistor and a control circuit installed in a plastic housing. The Hot Wire Air Flow Meter works on the principle that the hot wire and thermistor 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 Air Flow Meter.
The circuit is constructed so that the platinum hot wire and thermistor provide a bridge circuit, with the power transistor controlled so that the potential of A and B remains equal to maintain the set temperature.
If the Engine Control Module detects Diagnostic Trouble Code "P0100" it operates the fail safe function, keeping the ignition timing and injection volume constant and making it possible to drive the vehicle.

DIAGNOSTIC TROUBLE CODE DETECTING CONDITION
- Open or short in Mass Air Flow Meter circuit with engine speed 4,000 rpm or less.

TROUBLE AREA
- Open or short in mass air flow meter circuit.
- Mass air flow meter.
- Engine Control Module.

NOTE: After confirming Diagnostic Trouble Code "P0100" use the OBDII scan tool or LEXUS hand-held tester to confirm the Mass Air Flow ratio from "CURRENT DATA":

Mass Air Flow Value 0.0 gm/second.
- + B circuit open.
- VG circuit open or short.

Mass Air Flow Value 271.0 or more gm/second
- VG- circuit open.