Toyota RAV4 Service Manual: Mass air flow circuit range / performance problem

Description

Refer to dtc p0100 (see page es-86).

Monitor description

The maf meter is a sensor that measures the amount of air flowing through the throttle valve. The ecm uses this information to determine the fuel injection time and to provide an appropriate air-fuel ratio. Inside the maf meter, there is a heated platinum wire which is exposed to the flow of intake air. By applying a specific electrical current to the wire, the ecm heats it to a specific temperature. The flow of incoming air cools both the wire and an internal thermistor, affecting their resistance. To maintain a constant current value, the ecm varies the voltage applied to these components of the maf meter. The voltage level is proportional to the airflow through the sensor, and the ecm uses it to calculate the intake air volume.

The ecm monitors the average engine load value ratio to check the maf meter for malfunctions. The average engine load value ratio is obtained by comparing the average engine load calculated from the maf meter output to the average engine load estimated from the driving conditions, such as the engine speed and the throttle opening angle. If the average engine load value ratio is below the threshold value, the ecm determines that the intake air volume is low, and if the average engine load value ratio is above the threshold value, the ecm determines that the intake air volume is high.

If this is detected in 2 consecutive driving cycles, the mil is illuminated and a dtc is set.

Monitor strategy

Typical enabling conditions

Typical malfunction thresholds

Wiring diagram

Refer to dtc p0100 (see page es-88).

Confirmation driving pattern

Hint:

Performing this confirmation pattern will activate the mass air flow performance monitor.

1. Connect the intelligent tester to the dlc3.
2. Turn the ignition switch on.
3. Turn the tester on.
4. Clear dtcs (see page es-35).
5. Start the engine, and warm it up until the engine coolant temperature reaches 70°c (158°f) or higher.
6. Drive the vehicle at approximately 100 km/h (62 mph) for 20 seconds or more.
7. On the tester, select the following menu items: diagnosis / enhanced obd ii / dtc info / pending codes and check if any dtcs (any pending dtcs) are set.

Inspection procedure

Hint:

Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

1. Check any other dtcs output (in addition to dtc p0101)

1. Connect the intelligent tester to the dlc3.
2. Turn the ignition switch on.
3. Turn the tester on.
4. Select the following menu items: diagnosis / enhanced obd ii / dtc info / current codes.
5. Read dtcs.

Hint:

If any dtcs other than p0101 are output, troubleshoot those dtcs first.

2. Check air induction system

1. Check the air induction system for vacuum leakage.

Ok:

No leakage from air induction system.

3. Check pcv hose connections

Ok:

Pcv hose is connected correctly and is not damaged.

Replace mass air flow meter