Actron CP9087 - Manual (Page 48)

2-40
Testing Sensors
Section 2
Sensor operation (see tests on pages 2-43 through 2-44).
Poor connections at sensor or computer. Faulty sensor
wiring (open or short circuits). Airflow obstructions in
ductwork or clogged air filter. Binding pivot on vane
“door”. Air leaks around sensor or throttle body.
What to
Inspect
When to
Test
• Related trouble codes sent by computer.
• Driveability problems such as hard starting, rough idle,
stalling, hesitation, stumble, surging, knocking (ping-
ing), poor fuel economy, black exhaust smoke, backfir-
ing, catalytic converter overheating or no torque
converter lock-up.
Location
The sensor is mounted in the engine incoming air duct -
between the air cleaner and the throttle body.
How it is
used?
The computer needs to know incoming air flow to properly
adjust air/fuel mixture and ignition timing for varying
engine load and operating conditions.
What
is It?
This sensor sends a dc voltage signal to the computer
indicating the amount of air entering the engine. The
voltage signal increases as the air flow increases. The
sensor assembly has a pivoting door (“vane”) which is
opened by incoming air. The vane is connected to a
potentiometer (a variable resistor - like a dashboard
dimmer control) which generates the voltage signal. Some
sensor assemblies also contain an air temperature sensor
or a vane position switch (or both).
AIR FLOW
Vane Air Flow Sensors
Typical VAF Sensor
Referred to as Vane Air Flow
(VAF) sensor or Air Flow Meter