Volume Air Flow Sensor

Operation

The volume air flow sensor is incorporated within the air cleaner; it functions to convert the amount of engine air intake to pulse signals of a frequency proportional to the amount of engine air intake, and to input those/signals to the engine control module. The engine control module then, based upon those signals, calculates the amount of fuel injection, etc.

The power for the volume air flow sensor is supplied from the multiport fuel injection relay to the volume air flow sensor, and is grounded at the engine control module. The volume air flow sensor, by intermitting the flow of the 5V Voltage applied from the engine control module, produces pulse signals.


Troubleshooting Hints

HINT 1: If the engine sometimes stalls, try starting the engine and shaking the volume air flow sensor harness. If the engine then stalls, incorrect or improper contact of the volume air flow sensor connector is the probable cause.

Hint 2: If, when the ignition switch is switched ON (but the engine is not started), the volume air flow sensor output frequency is any value other than zero, a malfunction of the volume air flow sensor or of the engine control module is the probable cause.

Hint 3: If idling is possible even though the volume air flow sensor output frequency is deviated from the standard value, the cause is usually a malfunction other than of the volume air flow sensor.

Examples:

(1) The flow of air within the volume air flow sensor is disturbed. (Air duct disconnection or clogged air cleaner element)
(2) Incomplete combustion within a cylinder. (Malfunction of spark plugs, ignition coil, injectors, compression pressure, etc.)
(3) Air is taken into the intake manifold through a leaking gasket, etc.
(4) Incomplete close contact of the EGR valve seat.




Inspection









Harness Inspection


Using Oscilloscope

(1) Run the engine at idle speed





(2) Connect the probe to the oscilloscope pick-up point as shown in the circuit diagram, and check the wave form.