Position Sensor; Absolute Pressure (Map) And Baro Sensor; Mass Air Flow (Maf) Sensor - KNOVA KN 8056 Manual

Diagnosis of automotive Troubles
figure 17
Testing Procedure:
(1) The same as in the resistance testing method.
(2) When the general temperature of a heating
sensor rises, its resistance will drop. The
thermal resistance of the temperature sensor
of the automotive engine is generally less than
300 Ω.
3. Position Sensor (see figure 18)
Toyota Motor Throttle Position Sensor
figure 18
Signal Terminal
The position sensor is an electrometer or variable
resistance. It is used for the computer monitoring
of the position and direction of a mechanical
device. The typical position sensors include
throttle, exhaust recirculating EGR, blade air
flow and other sensors.
Testing Procedure:
(1) The same as in the resistance testing method.
(2) Connect the red and black test lead probes
respectively to the signal test terminal and
ground terminal. Refer to various kinds of
automotive servicing manuals for its position
and the resistance to be tested.

4. Absolute Pressure (MAP) and Baro Sensor

(see figure 19)
The MAP sensor is used to change a pressure
signal into a DC voltage or frequency one. All GM,
Chrysler, Honda and Toyota use DC voltage type
MAP sensors, while Ford uses frequency type
MAP sensors. Refer to relevant manuals for other
automotive manufacturers.
Heater
Temperature
Sensor
Red
Black
V+
Ground
Empty Foot
Black
MAP Type
Sensor
figure 19
Testing Procedure:
(1) Connect the DC voltage type MAP sensor in
the DC voltage testing method and set the
rotary switch of the meter to 20 VDC.
(2) Connect the frequency type MAP sensor in the
RPM x10 testing method and set the meter to
the number of cylinders in the automobile.
(3) Taking 4 cylinders (4CYL) for example, connect
the black test lead probe of the meter to the
ground terminal (i.e. ground strap connection)
and connect the red one as illustrated in figure
20.
(4) Turn on the ignition key but do not start the
engine.
Displayed Values:
DC Voltage Type Sensor:
In a vacuum state, the displayed value is generally
between 3 V and 5 V. (The details shall be based
on the parameters furnished by the supplier.)
Frequency Type Sensor:
In a vacuum state, the displayed value is generally
4770 RPM 5%. (This only applies to the MAP
sensor produced by Ford and the other sensors
shall be based on the parameters furnished by the
supplier.)
WARNING
• The reading becomes the actual RPM
only after it is multiplied by 10.
• Frequency = RPM/30. (This only applies to
4CYL.)
5. Mass Air Flow (MAF) Sensor (see figure 20)
The sensor converts the air flow into a DC voltage,
low frequency or high frequency signal. KN 8056
can only be used to test a DC voltage or low
frequency signal.
12
Red
To Computer