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Toyota Air Flow Sensors

Page history last edited by wilbo666 3 years, 9 months ago


 

Introduction

This page documents Toyota air flow sensors, often refereed to as AFM (Air Flow Meters) or MAF sensors (Mass Air Flow).

 

There are a number of different types of Toyota air flow sensors, including the older 'flap' style, Karman vortex and hot wire to name a few.

 

In general air flow meters are used to detect the mass of air that is entering an engine so that the correct amount of fuel can be injected. Internal combustion engines have a requirement for a specific ratio of air to fuel which is called the Air Fuel Ratio or AFR. If the air flow is measured then the required fuel can be calculated and then injected.

 

As the density of air changes across temperature it is logical to include an air temperature sensor as part of the air flow sensor so that the mass of air can be determined (it is the mass of air not the volume that is required for correct AFR calculations).

 

Hot Wire Mass Air Flow Sensor (5 Wire)

Operation of a hot wire MAF according to DENSO (a manufacture of Hot Wire MAFs) :

"A portion of the intake air from the air cleaner is bypassed into the hot-wire measurement area, where the intake airflow volume is measured. The hot-wire type MAF Sensor responds to temperature changes in the heating element. Changes in the resistance value and current of the heating element are converted into proportional voltage in the control circuit, and then sent to the ECU to calculate the amount of engine intake air volume."

 

This style of MAF comes in a number of different packages.

 

 

 

 

CAUTION: THERE ARE AT LEAST TWO DIFFERENT WIRING CONFIGURATIONS FOR TOYOTA 5 WIRE MAF SENSORS.

I suggest using an Ohmmeter to identify which MAF contacts are connected to the THA thermistor to identify the pinout of the AFM if in doubt.

i.e. early wiring will have a resistance of ~2.21kΩ to 2.69kΩ at 20°C (68°F) between pins 1 and 2.

i.e. later wiring will have a resistance of ~2.21kΩ to 2.69kΩ at 20°C (68°F) between pins 4 and 5.

 

 

JZS161 2JZGE before 07/2000 (Also JZS161 2JZGTE & JZA80 2JZGTE VVTi):

Pin Symbol Definition Input / Output
(To Sensor = Input)
(From Sensor = Output)
Description
1 THA
Air Temperature Sensor Output
This pin connects to a thermistor that is installed in the airflow sensor and outputs a voltage related to the air temperature to the engine ECU.
2 E2 Sensor Ground (Air Temperature Sensor)
Input The airflow meter has a separate ground for the air temperature thermistor. This pin is connected to sensor Ground inside the engine ECU.
3 EVG Mass Airflow Sensor Ground Input The airflow meter sensor has a separate signal ground to ensure a clear signal. This pin is connected to sensor Ground inside the engine ECU.
4 +B EFI Main Relay Switched Power Input
This pin supplies power to the airflow meter. This pin is connected to battery voltage (+12V) when the Main EFI Relay is energised via the engine ECU pin M-REL pin.  
5 VG Engine Airflow Output This pin connects to the signal output of the airflow sensor and output a voltage related to the airflow to the engine ECU.

 

JZS161 2JZGE after 07/2000 (Also JZS171 1JZGTE):

Pin Symbol Definition Input / Output
(To Sensor = Input)
(From Sensor = Output)
Description
1
+B EFI Main Relay Switched Power Input
This pin supplies power to the airflow meter. This pin is connected to battery voltage (+12V) when the Main EFI Relay is energised via the engine ECU pin M-REL pin.  
2 EVG (or E2G) Mass Airflow Sensor Ground Input The airflow meter sensor has a separate signal ground to ensure a clear signal. This pin is connected to sensor Ground inside the engine ECU.
3 VG Engine Airflow Output This pin connects to the signal output of the airflow sensor and output a voltage related to the airflow to the engine ECU.
4 THA
Air Temperature Sensor Output
This pin connects to a thermistor that is installed in the airflow sensor and outputs a voltage related to the air temperature to the engine ECU.
5 E2 Sensor Ground (Air Temperature Sensor)
Input The airflow meter has a separate ground for the air temperature thermistor. This pin is connected to sensor Ground inside the engine ECU.

 

 

 

References

 

http://en.wikipedia.org/wiki/Mass_flow_sensor

http://www.denso-am.eu/products/automotive-aftermarket/engine-management-systems/mass-air-flow-sensors/how-they-work/

 

 

 

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