Troubleshooting

P0100 Mass Air Flow Circuit Malfunction





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.




DETECTING CONDITIONS
If the ECM detects DTC P0100 it operates the fail-safe function, keeping the ignition timing and injection volume constantly and making it possible to drive the vehicle.






HINT: After confirming DTC P0100, use the OBD II scan tool or LEXUS hand-held tester to confirm the mass air flow ratio from the CURRENT DATA.




WIRING DIAGRAM

Step 1:

INSPECTION PROCEDURE

HINT: Read freeze frame data using LEXUS hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.