Dtc P0100 Mass Air Flow Circuit Malfunction

Engine. Lexus Gs430, Gs300. Uzs190 Grs190
3Uz-Fe Engine Control System. Lexus Gs430, Gs300. Uzs190 Grs190

DESCRIPTION

MONITOR DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

READ DATA LIST (MASS AIR FLOW RATE)

INSPECT MASS AIR FLOW METER (POWER SOURCE VOLTAGE)

INSPECT ECM (VG VOLTAGE)

CHECK WIRE HARNESS (MASS AIR FLOW METER - ECM)

CHECK WIRE HARNESS (MASS AIR FLOW METER - INTEGRATION RELAY)

INSPECT ECM (SENSOR GROUND)

CHECK WIRE HARNESS (MASS AIR FLOW METER - ECM)

DTC P0100 Mass Air Flow Circuit Malfunction

DTC P0102 Mass Air Flow Circuit Low

DTC P0103 Mass Air Flow Circuit High


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.

Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System. Dtc P0100 Mass Air Flow Circuit Malfunction


DTC No.
DTC Detection Condition
Trouble Area
P0100
Open or short in MAF meter circuit for 3 seconds
(1 trip detection logic)
  1. Open or short in MAF meter circuit
  2. MAF meter
  3. ECM
P0102
Open or short in MAF meter circuit for 3 seconds
(1 trip detection logic)
Same as DTC No. P0100
P0103
Open to EVG in MAF meter circuit for 3 seconds
Short to +B in MAF meter circuit for 3 seconds
(1 trip detection logic)
Same as DTC No. P0100

MONITOR DESCRIPTION

If there is a defect in the MAF meter or an open or short circuit, the voltage level will deviate outside the normal operating range. The ECM interprets this deviation as a defect in the MAF meter and sets a DTC.
Example:
When the sensor output voltage is less than 0.2 V or more than 4.9 V and if either condition continues for more than 3 seconds, the ECM will set a DTC.
This monitor runs for 3 seconds (the first 3 seconds of engine idle) after the engine is started (1 trip detection logic).
HINT:
After confirming DTC P0100, P0102 or P0103, use the intelligent tester to confirm the MAF (to reach the MAF menu: Powertrain / Engine / Data List / Primary).

MAF (gm/s)
Malfunction
0.0
  1. MAF meter power source circuit open
  2. VG circuit open or short
271.0 or more
E2G circuit open

WIRING DIAGRAM


Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System. Dtc P0100 Mass Air Flow Circuit Malfunction


INSPECTION PROCEDURE

HINT:
Read freeze frame data using the intelligent tester. 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.
1.READ DATA LIST (MASS AIR FLOW RATE)

  1. Connect the intelligent tester to the DLC3.

  1. Allow the engine to idle.

  1. Enter the following menus: Powertrain / Engine / Data List / Primary / MAF.

  1. Read the MAF value.


Result:

Mass Air Flow (g/second)
Proceed to
0.0
A
271.0 or more
B
MAF rate greater than 1 but less than 270.0*
C
HINT:
*: The value must change when the throttle valve is opened or closed.


B
Go to step 6

C
CHECK FOR INTERMITTENT PROBLEMS
A


2.INSPECT MASS AIR FLOW METER (POWER SOURCE VOLTAGE)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System. Dtc P0100 Mass Air Flow Circuit Malfunction

  1. Turn the engine switch on (IG).

  1. Disconnect the E42 MAF meter connector.

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

    Standard voltage:
    Tester Connection
    		Specified Condition
    E42-1 (+B) - Body ground
    		9 to 14 V


NG
Go to step 5
OK


3.INSPECT ECM (VG VOLTAGE)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System. Dtc P0100 Mass Air Flow Circuit Malfunction

  1. Start the engine.

  1. Measure the voltage of the E6 ECM connector.

    HINT:
    Move the shift lever to P or N and turn the A/C switch OFF.
    Standard voltage:
    Tester Connection
    		Condition
    		Specified Condition
    E6-27 (VG) - E6-26 (E2G)
    		Engine is idling
    		0.5 to 3.0 V


OK
REPLACE ECM
NG


4.CHECK WIRE HARNESS (MASS AIR FLOW METER - ECM)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System. Dtc P0100 Mass Air Flow Circuit Malfunction

  1. Disconnect the E42 MAF meter connector.

  1. Disconnect the E6 ECM connector.

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

    Standard resistance:
    Tester Connection
    		Specified Condition
    E42-2 (E2G) - E6-26 (E2G)
    		Below 1 Ω
    E42-3 (VG) - E6-27 (VG)
    		Below 1 Ω
    E42-2 (E2G) or E6-26 (E2G) - Body ground
    		10 kΩ or higher
    E42-3 (VG) or E6-27 (VG) - Body ground
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK

REPLACE MASS AIR FLOW METER

5.CHECK WIRE HARNESS (MASS AIR FLOW METER - INTEGRATION RELAY)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System. Dtc P0100 Mass Air Flow Circuit Malfunction

  1. Disconnect the E42 MAF meter connector.

  1. Remove the integration relay from the engine room No. 2 junction block.

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

    Standard resistance:
    Tester Connection
    		Specified Condition
    E42-1 (+B) - 2A-8
    		Below 1 Ω
    E42-1 (+B) or 2A-8 - Body ground
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK

CHECK ECM POWER SOURCE CIRCUIT

6.INSPECT ECM (SENSOR GROUND)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System. Dtc P0100 Mass Air Flow Circuit Malfunction

  1. Measure the resistance of the ECM connector.

    Standard resistance:
    Tester Connection
    		Specified Condition
    E6-26 (E2G) - Body ground
    		Below 1 Ω


NG
REPLACE ECM
OK


7.CHECK WIRE HARNESS (MASS AIR FLOW METER - ECM)
Lexus Gs430, Gs300. Uzs190 Grs190.3Uz-Fe Engine Control System.Sfi System. Dtc P0100 Mass Air Flow Circuit Malfunction

  1. Disconnect the E42 MAF meter connector.

  1. Disconnect the E6 ECM connector.

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

    Standard resistance:
    Tester Connection
    		Specified Condition
    E42-2 (E2G) - E6-26 (E2G)
    		Below 1 Ω
    E42-3 (VG) - E6-27 (VG)
    		Below 1 Ω
    E42-2 (E2G) or E6-26 (E2G) - Body ground
    		10 kΩ or higher
    E42-3 (VG) or E6-27 (VG) - Body ground
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK

REPLACE MASS AIR FLOW METER