Brand:

Toyota

Model Name:

Yaris NCP90 91 92 93

Manual:

Repair Manual

Section:

1Nz-Fe Engine Control System

Title:

Sfi System

  1. Description

  2. Wiring diagram

  3. Inspection procedure

  4. Read value using intelligent tester (mass air flow rate)

  5. Inspect mass air flow meter (power source voltage)

  6. Inspect mass air flow meter (vg voltage)

  7. Check harness and connector (mass air flow meter - ecm)

  8. Check harness and connector (mass air flow meter - integration relay)

  9. Check harness and connector (sensor ground)

  10. Check harness and connector (mass air flow meter - ecm)

DTC P0100 Mass or Volume Air Flow Circuit

DTC P0102 Mass or Volume Air Flow Circuit Low Input

DTC P0103 Mass or Volume Air Flow Circuit High Input


​

DESCRIPTION

The Mass Air Flow (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 the 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 given 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 in 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 circuit is constructed so that the platinum hot wire and the temperature sensor create a bridge circuit, and the power transistor is controlled so that the potentials of A and B remain equal to maintain the predetermined temperature.
HINT:
When any of these DTCs are set, the ECM enters fail-safe mode. During fail-safe mode, the ignition timing is calculated by the ECM, according to the engine RPM and throttle valve position. Fail-safe mode continues until a pass condition is detected.

Open or short in MAF meter circuit Yaris


DTC No.
DTC Detection Conditions
Trouble Areas
P0100
MAF meter voltage less than 0.2 V, or more than 4.9 V for 3 seconds
(1 trip detection logic)
  1. Open or short in MAF meter circuit
  2. MAF meter
  3. ECM
P0102
MAF meter voltage less than 0.2 V for 3 seconds
(1 trip detection logic)
P0103
MAF meter voltage more than 4.9 V for 3 seconds
(1 trip detection logic)

HINT:
When any of these DTCs are set, check the air-flow rate by selecting the following menu items on an intelligent tester: Powertrain / Engine and ECT / Data List / MAF.

Mass Air Flow Rate (g/sec)
Malfunctions
Approximately 0.0
  1. Open in Mass Air Flow (MAF) meter power source circuit
  2. Open or short in VG circuit
271.0 or more
  1. Open in EVG circuit

WIRING DIAGRAM


Connect an intelligent tester to the DLC3. Yaris


INSPECTION PROCEDURE

HINT:
Read freeze frame data using an intelligent tester. Freeze frame data record 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.READ VALUE USING INTELLIGENT TESTER (MASS AIR FLOW RATE)

  1. Connect an intelligent tester to the DLC3.

  1. Start the engine and turn the tester on.

  1. Select the following menu items: Powertrain / Engine and ECT / Data List / MAF.

  1. Read the values displayed on the tester.

    Result:
    Mass Air Flow Rate (g/sec)
    		Proceed To
    0.0
    		A
    271.0 or more
    		B
    Between 1.0 and 270.0 (*1)
    		C
    *1: The value must be changed when the throttle valve is open or closed with the engine running.


Bnext
Go to step 6

Cnext
CHECK FOR INTERMITTENT PROBLEMS (Click here)
A
next down

2.INSPECT MASS AIR FLOW METER (POWER SOURCE VOLTAGE)
Disconnect the C26 Mass Air Flow (MAF) meter connector. Yaris

  1. Disconnect the C26 Mass Air Flow (MAF) meter connector.

  1. Turn the ignition switch to ON.

  1. Measure the voltage between the terminal of the wire harness side connector and body ground.

    Standard voltage:
    Tester Connections
    		Specified Conditions
    +B (C26-1) - Body ground
    		9 to 14 V

  1. Reconnect the MAF meter connector.



NGnext
Go to step 5
OK
next down

3.INSPECT MASS AIR FLOW METER (VG VOLTAGE)
Output voltage inspection.Disconnect the C26 MAF meter connector.Apply battery voltage across terminals +B and E2G.Connect the positive (+) tester probe to terminal VG, and negative (-) tester probe to terminal E2G.Check the voltage.Standard voltage:Tester ConnectionsSpecified ConditionsVG (3) - E2G (2)0.2 to 4.9 VReconnect the MAF meter connector. Yaris

  1. Output voltage inspection.

    1. Disconnect the C26 MAF meter connector.

    2. Apply battery voltage across terminals +B and E2G.

    3. Connect the positive (+) tester probe to terminal VG, and negative (-) tester probe to terminal E2G.

    4. Check the voltage.

      Standard voltage:
      Tester Connections
      		Specified Conditions
      VG (3) - E2G (2)
      		0.2 to 4.9 V

    5. Reconnect the MAF meter connector.



NGnext
REPLACE MASS AIR FLOW METER (Click here)
OK
next down

4.CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)
Disconnect the C26 MAF meter connector. Yaris

  1. Disconnect the C26 MAF meter connector.

  1. Disconnect the C20 ECM connector.

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    VG (C26-3) - VG (C20-118)
    		Below 1 Ω
    E2G (C26-2) - E2G (C20-116)
    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    VG (C26-3) or VG (C20-118) - Body ground
    		10 kΩ or higher

  1. Reconnect the MAF meter connector.

  1. Reconnect the ECM connector.



NGnext
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK
next down
REPLACE ECM (Click here)

5.CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - INTEGRATION RELAY)
Disconnect the C26 MAF meter connector. Yaris

  1. Disconnect the C26 MAF meter connector.

  1. Remove the integration relay from the engine room relay block.

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    +B (C26-1) - 1A-4
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    +B (C26-1) or 1A-4 - Body ground
    		10 kΩ or higher

  1. Reconnect the MAF meter connector.

  1. Reinstall the integration relay.



NGnext
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK
next down
CHECK ECM POWER SOURCE CIRCUIT (Click here)

6.CHECK HARNESS AND CONNECTOR (SENSOR GROUND)
  1. Disconnect the C26 MAF meter connector. Yaris

  2. Disconnect the C26 MAF meter connector.

  1. Check the resistance.

    Standard resistance:
    Tester Connections
    		Specified Conditions
    E2G (C26-2) - Body ground
    		Below 1 Ω

  1. Reconnect the MAF meter connector.



OKnext
REPLACE MASS AIR FLOW METER (Click here)
NG
next down

7.CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)
Disconnect the C26 MAF meter connector. Yaris

  1. Disconnect the C26 MAF meter connector.

  1. Disconnect the C20 ECM connector.

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    VG (C26-3) - VG (C20-118)
    		Below 1 Ω
    E2G (C26-2) - E2G (C20-116)
    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    VG (C26-3) or VG (C20-118) - Body ground
    		10 kΩ or higher

  1. Reconnect the MAF meter connector.

  1. Reconnect the ECM connector.



NGnext
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK
next down
REPLACE ECM (Click here)