Toyota Tundra Service Manual: Mass Air Flow Circuit Low (P0102,P0103)

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 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 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 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 RPM and throttle valve position. Fail-safe mode continues until a pass condition is detected.

HINT:

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

MONITOR DESCRIPTION

If there is a defect in the MAF meter or an open or short circuit, the voltage level deviates from the normal operating range. The ECM interprets this deviation as a malfunction in the MAF meter and stores a DTC.

Example:

When the sensor output voltage remains at less than 0.2 V, or more than 4.9 V for more than 3 seconds, the ECM stores a DTC.

If the malfunction is not repaired successfully, a DTC is stored 3 seconds after the engine is next started.

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

COMPONENT OPERATING RANGE

CONFIRMATION DRIVING PATTERN

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the Techstream on.
3. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
4. Turn the ignition switch off and wait for at least 30 seconds.
5. Turn the ignition switch to ON and turn the Techstream on [A].
6. Start the engine.
7. Idle the engine for 5 seconds [B].
8. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [C].
9. Read the pending DTCs.

   HINT:

   • If a pending DTC is output, the system is malfunctioning.
   • If a pending DTC is not output, perform the following procedure.
10. Run the engine at an engine speed of 4000 rpm or more for 5 seconds [D].
11. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [E].
12. Read the pending DTCs.

    HINT:

    • If a pending DTC is output, the system is malfunctioning.
    • If a pending DTC is not output, perform the following procedure.
13. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
14. Input the DTC: P0102 or P0103.
15. Check the DTC judgment result.

    Techstream Display	Description
    NORMAL	DTC judgment completed System normal
    ABNORMAL	DTC judgment completed System abnormal
    INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
    N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

    HINT:

    • If the judgment result shows NORMAL, the system is normal.
    • If the judgment result shows ABNORMAL, the system has a malfunction.
    • If the judgment result shows INCOMPLETE or N/A, perform steps [B] through [C] again.
16. If no pending DTC is output, perform a universal trip and check for permanent DTCs (See page ).

    HINT:

    • If a permanent DTC is output, the system is malfunctioning.
    • If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

Read freeze frame data using the Techstream. 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.

PROCEDURE

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read DTCs.

B

GO TO STEP 5

A

(a) Disconnect the mass air flow meter connector.

(b) Turn the ignition switch to ON.

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

Standard Voltage:

NG

GO TO STEP 7

OK

(a) Disconnect the mass air flow meter connector.

(b) Disconnect the ECM connector.

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

Standard Resistance:

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

(a) Inspect the mass air flow meter, referring to the On-vehicle inspection for mass air flow meter (See page ).

(b) Inspect the mass air flow meter, referring to the inspection for mass air flow meter (See page ).

(c) Inspect the function of the mass air flow meter.

(1) Connect the Techstream to the DLC3.

(2) Turn the ignition switch to ON.

(3) Turn the Techstream on.

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

(5) Start the engine.

(6) Check that the MAF value changes when the engine is raced.

OK:

The reading changes.

HINT:

Perform "Inspection After Repair" after replacing the mass air flow meter (See page ).

OK

REPLACE ECM

NG

REPLACE MASS AIR FLOW METER

(a) Disconnect the mass air flow meter connector.

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

Standard Resistance:

HINT:

Perform "Inspection After Repair" after replacing the mass air flow meter (See page ).

OK

REPLACE MASS AIR FLOW METER

NG

(a) Disconnect the mass air flow meter connector.

(b) Disconnect the ECM connector.

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

Standard Resistance:

OK

REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

(a) Disconnect the mass air flow meter connector.

(b) Remove the integration relay from the engine room relay block.

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

Standard Resistance:

OK

CHECK ECM POWER SOURCE CIRCUIT

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR