P0101

3UZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0101: Mass Air Flow Circuit Range / Performance Problem

DTC P0101 - Mass Air Flow Circuit Range / Performance Problem

DESCRIPTION

The Mass Air Flow (MAF) meter measures the amount of air flowing through the throttle valve. The ECM uses this information to determine the fuel injection time and provide a proper air-fuel ratio. Inside the MAF meter, there is a heated platinum wire exposed to the flow of intake air.
By applying a specific current to the wire, the ECM heats this wire to a given temperature. The flow of incoming air cools the wire and an internal thermistor, affecting their resistance. To maintain a constant current value, the ECM varies the voltage applied to these components in the MAF meter. The voltage level is proportional to the air flow through the sensor. The ECM interprets this voltage as the intake air amount.
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.










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 the wire and internal thermistor. 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

ALL:





TYPICAL MALFUNCTION THRESHOLDS





COMPONENT OPERATING RANGE





WIRING DIAGRAM





CONFIRMATION DRIVING PATTERN
HINT: Performing this confirmation pattern will activate the mass air flow performance monitor.





1 Connect the Techstream to the DLC3.
2 Turn the ignition switch ON.
3 Turn the tester ON.
4 Clear DTCs DTC Check / Clear.
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 62 mph (100 km/h) for 20 seconds or more.
7 On the tester, enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending; and then check if any DTCs (any pending DTCs) are set.

INSPECTION PROCEDURE
HINT: Read freeze frame data using the Techstream. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.

PROCEDURE

1. CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0101)
(a) Connect the Techstream to the DLC3.
(b) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(c) Read the DTCs.
Result:






B -- GO TO RELEVANT DTC CHART
A -- Continue to next step.
2. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leakage.
OK:
No leakage from air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
3. CHECK VENTILATION HOSE CONNECTIONS
OK:
Ventilation hose is connected correctly and is not damaged.
NG -- REPAIR OR REPLACE VENTILATION HOSE
OK -- REPLACE MASS AIR FLOW METER