Lexus IS250 · Service Manual ENGINE

P0100

Diagnostic trouble codes

DESCRIPTION

The Mass Air Flow (MAF) meter is a sensor that measures the amount of air flowing through the valve.
The ECM uses this information to determine the fuel injection time and to prove 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 provide 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.

A094565E07
DTC No.
 DTC Detection Condition
 Trouble Area
P0100
 Open or short in Mass Air Flow (MAF) meter circuit for 3 seconds
  1. Open or short in MAF meter circuit
  2. MAF meter
  3. ECM
P0102
 Open in Mass Air Flow (MAF) meter circuit for 3 seconds
  1. Open in MAF meter circuit
  2. Short in MAF meter circuit
  3. MAF meter
  4. ECM
P0103
 Short in Mass Air Flow (MAF) meter circuit for 3 seconds
  1. Short in MAF meter circuit (+B circuit)
  2. MAF meter
  3. ECM

HINT:
When any of these DTCs are set, check the air-flow rate by entering the following menus on the intelligent tester: Power train / Engine / Data List / MAF.
Mass Air Flow Rate (gm/s)
 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

A117876E01

INSPECTION PROCEDURE

HINT:
Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions 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 (Click here).


1. READ VALUE OF MASS AIR FLOW METER (MAF)

  1. Connect the intelligent tester to the DLC3.

  1. Start the engine.

  1. Turn the tester ON.

  1. Enter the following menus: Power train / Engine / Data List / MAF.

  1. Read the values displayed on the tester.

    Result:
    Mass Air Flow Rate (gm/s)
    		 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.



 B
Go to step 6

C
CHECK FOR INTERMITTENT PROBLEMS
A


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

  1. A054396E66
    Disconnect the E29 Mass Air Flow (MAF) meter connector.

  1. Turn the engine switch on (IG).

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

    Standard voltage:
    Tester Connection
    		 Specified Condition
    +B (E29-3) - Body ground
    		 9 to 14 V

  1. Reconnect the MAF meter connector.



 NG
Go to step 5
OK


3. INSPECT ECM (VG VOLTAGE)

  1. A122885E08
    Start the engine.

  1. Measure the voltage of the E5 ECM connector.

    HINT:
    The transmission gear selector lever should be in the P or N position and the A/C switch should be turned OFF.

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    VG (E5-27) - E2G (E5-26)
    		 Engine idling
    		 0.5 to 3.0 V



OK
REPLACE ECM
NG


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

  1. A107705E06
    Disconnect the E29 MAF meter connector.

  1. Disconnect the E5 ECM connector.

  1. Measure the resistance of the wire harness side connector.

    Standard resistance (Check for open):
    Tester Connection
    		 Specified Condition
    VG (E29-5) - VG (E5-27)
    		 Below 1 Ω
    E2G (E29-4) - E2G (E5-26)
    		 Below 1 Ω

    Standard resistance (Check for short):
    Tester Connection
    		 Specified Condition
    VG (E29-5) or VG (E5-27) - Body ground
    		 10 kΩ or higher

  1. Reconnect the MAF meter connector.

  1. Reconnect the ECM connector.



 NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE MASS AIR FLOW METER

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

  1. A107732E08
    Inspect the EFI No. 2 fuse.

    1. Remove the EFI No. 2 fuse from the engine room No.2 relay block.

    2. Check the EFI No. 2 fuse resistance.

      Standard resistance:
      Below 1 Ω

    3. Reinstall the EFI No. 2 fuse.

  1. Disconnect the E29 MAF meter connector.

  1. Remove the integration relay from the engine room J/B and R/B No. 2.

  1. Measure the resistance of the wire harness side connector.

    Standard resistance (Check for open):
    Tester Connection
    		 Specified Condition
    +B (E29-3) - 2A-8
    		 Below 1 Ω

    Standard resistance (Check for short):
    Tester Connection
    		 Specified Condition
    +B (E29-3) or 2A-8 - Body ground
    		 10 kΩ or higher

  1. Reconnect the MAF meter connector.

  1. Reinstall the integration relay.



 NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

CHECK ECM POWER SOURCE CIRCUIT

6. INSPECT ECM (SENSOR GROUND)

  1. A122885E09
    Measure the resistance of the ECM connector.

    Standard resistance:
    Tester Connection
    		 Specified Condition
    E2G (E5-26) - Body ground
    		 Below 1 Ω



NG
REPLACE ECM
OK


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

  1. A107705E06
    Disconnect the E29 MAF meter connector.

  1. Disconnect the E5 ECM connector.

  1. Measure the resistance of the wire harness side connector.

    Standard resistance (Check for open):
    Tester Connection
    		 Specified Condition
    VG (E29-5) - VG (E5-27)
    		 Below 1 Ω
    E2G (E29-4) - E2G (E5-26)
    		 Below 1 Ω

    Standard resistance (Check for short):
    Tester Connection
    		 Specified Condition
    VG (E29-5) or VG (E5-27) - Body ground
    		 10 kΩ or higher

  1. Reconnect the MAF meter connector.

  1. Reconnect the ECM connector.



 NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE MASS AIR FLOW METER


← P0088P0110 →