Toyota FJ Cruiser (GSJ 10, 15 series). Instruction - part 35

1GR-FE ENGINE CONTROL SYSTEM  –  SFI SYSTEM

ES–95

ES

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 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.

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

DTC No.

DTC Detection Conditions

Trouble Areas

P0100

Open or short in Mass Air Flow (MAF) meter circuit for 3 
seconds
(1 trip detection logic)

•

Open or short in MAF meter circuit

•

MAF  meter

•

ECM

P0102

Open in Mass Air Flow (MAF) meter circuit for 3 seconds
(1 trip detection logic)

•

Open in MAF meter circuit

•

Short in ground circuit

•

MAF  meter

•

ECM

P0103

Short in Mass Air Flow (MAF) meter circuit for 3 seconds
(1 trip detection logic)

•

Short in MAF meter circuit (+B circuit)

•

MAF  meter

•

ECM

Temperature Sensor 
(Thermistor)

Temperature Sensor (Thermistor)

Power Transistor

Piatinum Hot Wire

Piatinum Hot Wire (Heater)

Output Voltage

+B

B

A

A115747E01

ES–96

1GR-FE ENGINE CONTROL SYSTEM  –  SFI SYSTEM

ES

HINT:
When any of these DTCs are set, check the air-flow rate by selecting the following menu items on an 
intelligent tester: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / 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 sets a DTC.
Example:
When the sensor voltage output remains less than 0.2 V, or more than 4.9 V, for more than 3 seconds, the 
ECM sets a DTC.
If the malfunction is not repaired successfully, a DTC is set 3 seconds after the engine is next started.

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

P0100:

P0102:

P0103:

COMPONENT OPERATING RANGE

Mass Air Flow Rate (g/sec)

Malfunctions

Approximately 0.0

•

Open in Mass Air Flow (MAF) meter power source circuit

•

Open or short in VG circuit

271.0 or more

•

Open in EVG circuit

Related DTCs

P0100: Mass air flow meter range check (Fluctuating)
P0102: Mass air flow meter range check (Low voltage)
P0103: Mass air flow meter range check (High voltage)

Required Sensors/Components (Main)

MAF meter

Required Sensors/Components (Related)

Crankshaft position sensor

Frequency of Operation

Continuous

Duration

3 seconds

MIL Operation

Immediate: Engine RPM less than 4,000 rpm
2 driving cycles: Engine RPM 4,000 rpm or more

Sequence of Operation

None

Monitor runs whenever following DTCs not present

None

Mass air flow meter voltage

Less than 0.2 V or more than 4.9 V

Mass air flow meter voltage

Less than 0.2 V

Mass air flow meter voltage

More than 4.9 V

Mass air flow meter voltage

Between 0.2 V and 4.9 V

1GR-FE ENGINE CONTROL SYSTEM  –  SFI SYSTEM

ES–97

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WIRING DIAGRAM

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.

(a) Connect an intelligent tester to the DLC3.
(b) Start the engine.
(c) Turn the tester ON.
(d) Select the following menu items: DIAGNOSIS / 

ENHANCED OBD II / DATA LIST / PRIMARY / MAF.

(e) Read the values displayed on the tester.

Result

1

READ VALUE USING INTELLIGENT TESTER (MASS AIR FLOW RATE)

Battery

EFI

EFI

EFI No. 2

ECM

VG

E2G

MREL

Mass Air Flow Meter

3

1

5

2

1

3

2

1

2

2

1

E47

8

B1

B1

30

29

B13

A133457E01

Mass Air Flow Rate (g/sec)

Proceed to

0.0

A

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1GR-FE ENGINE CONTROL SYSTEM  –  SFI SYSTEM

ES

*

1: The value must be changed when the throttle valve is 

open or closed.

B

C

A

(a) Disconnect the B13 Mass Air Flow (MAF) meter 

connector.

(b) Turn the ignition switch ON.
(c) Measure the voltage between the terminal of the wire 

harness side connector and body ground.
Standard Voltage

(d) Reconnect the MAF meter connector.

NG

OK

(a) Start the engine.
(b) Measure the voltage between the terminals of the B1 

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

OK

NG

271.0 or more

B

Between 1.0 and 270.0 (

*

1)

C

Mass Air Flow Rate (g/sec)

Proceed to

              Go to step 6

CHECK FOR INTERMITTENT PROBLEMS

2

INSPECT MASS AIR FLOW METER (POWER SOURCE VOLTAGE)

5

4

3

2

1

Front View

Wire Harness Side:

MAF Meter Connector

B13

+B

A107942E07

Tester Connections

Specified Conditions

+B (B13-1) - Body ground

11 to 14 V

              Go to step 5

3

INSPECT ECM (VG VOLTAGE)

VG (+)

ECM Connector

B1

E2G (-)

A115970E16

Tester Connections

Conditions

Specified Conditions

VG (B1-30) - E2G (B1-29)

Engine idling

0.5 to 3.0 V

REPLACE ECM (See page 

ES-446

)