SFI SYSTEM, Diagnostic DTC:P0102 and P0103

DTC Code DTC Name
P0102 Mass Air Flow Circuit Low
P0103 Mass Air Flow Circuit High

DESCRIPTION

The mass air flow 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 mass air flow 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 mass air flow meter. The voltage level is proportional to the air flow 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.

Tip:

When either of these DTCs is stored, the ECM enters fail-safe mode. During fail-safe mode, the ignition timing is calculated by the ECM, according to the engine speed and throttle valve position. Fail-safe mode continues until a pass condition is detected.

A202104E37

DTC No.

DTC Detection Condition

Trouble Area

P0102

The mass air flow meter voltage is below 0.2 V for 3 seconds (1 trip detection logic).

  • Open or short in mass air flow meter circuit

  • Mass air flow meter

  • ECM

P0103

The mass air flow meter voltage is higher than 4.9 V for 3 seconds (1 trip detection logic).

  • Open or short in mass air flow meter circuit

  • Mass air flow meter

  • ECM
Tip:

When either of these DTCs is output, check the air-flow rate by entering the following menus on the GTS: Powertrain / Engine and ECT / Data List / MAF.

Mass Air Flow Rate (gm/sec.)

Malfunction

Approximately 0.0

  • Open in mass air flow meter power source circuit

  • Open or short in VG circuit

271.0 or more

  • Open in E2G circuit

WIRING DIAGRAM

A342927E01

CAUTION / NOTICE / HINT

Note:

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

Tip:

Read freeze frame data using the GTS. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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.

PROCEDURE

  1. CHECK DTC OUTPUT

    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

    5. Read the DTC.

      Table 1. Result

      Result

      Proceed to

      DTC P0102 is output

      A

      DTC P0103 is output

      B

    CHECK HARNESS AND CONNECTOR (SENSOR GROUND)Click here

  2. INSPECT MASS AIR FLOW METER (POWER SOURCE VOLTAGE)

    1. U121304E02

      Disconnect the mass air flow meter connector.

    2. Turn the ignition switch to ON.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection

      Switch Condition

      Specified Condition

      C3-3 (+B) - Body ground

      Ignition switch ON

      11 to 14 V
      Table 2. Text in Illustration

      *a

      Front view of wire harness connector

      (to Mass Air Flow Meter)

    4. Reconnect the mass air flow meter connector.

    CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - INTEGRATION RELAY)Click here

  3. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)

    1. Disconnect the mass air flow meter connector.

    2. Disconnect the ECM connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Open)

      Tester Connection

      Condition

      Specified Condition

      C3-5 (VG) - C111-137 (VG)

      Always

      Below 1 Ω

      C3-4 (E2G) - C111-104 (E2G)

      Always

      Below 1 Ω

      Standard Resistance (Check for Short)

      Tester Connection

      Condition

      Specified Condition

      C3-5 (VG) or C111-137 (VG) - Body ground

      Always

      10 kΩ or higher

    4. Reconnect the mass air flow meter connector.

    5. Reconnect the ECM connector.

    REPAIR OR REPLACE HARNESS OR CONNECTOR (MASS AIR FLOW METER - ECM)

  4. INSPECT MASS AIR FLOW METER

    1. Perform On-vehicle Inspection (Click here).

    2. Perform Inspection (Click here).

    3. Inspect the function of the mass air flow meter.

      1. Connect the GTS to the DLC3.

      2. Turn the ignition switch to ON.

      3. Turn the GTS on.

      4. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.

      5. Start the engine.

      6. Check that the reading of the mass air flow meter changes when the engine is raced.

        OK

        The reading changes.

        Tip:

        Perform "Inspection After Repair" after replacing the mass air flow meter (Click here).

    REPLACE ECM

    (Click here)

    REPLACE MASS AIR FLOW METER

    (Click here)

  5. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - INTEGRATION RELAY)

    1. Disconnect the mass air flow meter connector.

    2. Remove the integration relay (EFI MAIN relay) from the engine room No. 1 relay block.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Open)

      Tester Connection

      Condition

      Specified Condition

      C3-3 (+B) - 1B-4

      Always

      Below 1 Ω

      Standard Resistance (Check for Short)

      Tester Connection

      Condition

      Specified Condition

      C3-3 (+B) or 1B-4 - Body ground

      Always

      10 kΩ or higher

    4. Reconnect the mass air flow meter connector.

    5. Reinstall the integration relay.

    GO TO ECM POWER SOURCE CIRCUIT

    (Click here)

    REPAIR OR REPLACE HARNESS OR CONNECTOR (MASS AIR FLOW METER - INTEGRATION RELAY)

  6. CHECK HARNESS AND CONNECTOR (SENSOR GROUND)

    1. Disconnect the mass air flow meter connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Open)

      Tester Connection

      Condition

      Specified Condition

      C3-4 (E2G) - Body ground

      Always

      Below 1 Ω
      Tip:

      Perform "Inspection After Repair" after replacing the mass air flow meter (Click here).

    3. Reconnect the mass air flow meter connector.

    REPLACE MASS AIR FLOW METER

    (Click here)

  7. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)

    1. Disconnect the mass air flow meter connector.

    2. Disconnect the ECM connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Open)

      Tester Connection

      Condition

      Specified Condition

      C3-4 (E2G) - C111-104 (E2G)

      Always

      Below 1 Ω

      Standard Resistance (Check for Short)

      Tester Connection

      Condition

      Specified Condition

      C3-4 (E2G) or C111-104 (E2G) - Body ground

      Always

      10 kΩ or higher

    4. Reconnect the mass air flow meter connector.

    5. Reconnect the ECM connector.

    REPLACE ECM

    (Click here)

    REPAIR OR REPLACE HARNESS OR CONNECTOR (MASS AIR FLOW METER - ECM)