Actron AutoTroubleShooter CP7677 - Manual (Page 30)

30
Position Type Sensors
Position sensors are potentiometers or
a type of variable resistor. They are
used by the computer to determine po-
sition and direction of movement of a
mechanical device. Typical position sen-
sor applications are throttle position
sensors, EGR valve position sensors,
and vane air flow sensors.
Test Procedure (see Fig. 33):
• If multimeter overranges on larg-
est range, then sensor is an open
circuit and is defective.
7. Move RED test lead to sensor SIG-
NAL pin.
• Refer to vehicle service manual for
location of sensor SIGNAL pin.
8. Operate Sensor.
Fig. 33
1. Insert BLACK test lead into COM
test lead jack.
2. I n s e r t R E D t e s t l e a d i n t o
test lead jack.
3. Disconnect wiring harness from
sensor.
4. Connect Test Leads.
• Connect RED test lead to sensor
POWER pin.
• Connect BLACK test lead to sen-
sor GROUND pin.
• Refer to vehicle service manual for
location of sensor POWER and
GROUND pins.
5. Turn multimeter rotary switch to
20K
Ω
range.
6. View and record reading on dis-
play.
• Display should read some resis-
tance value.
• If multimeter is overranging, adjust
the range accordingly. (See Set-
ting the Range on page 6.)
Typical Toyota Throttle
Position Sensor
Red Black
POWER GROUND
SIGNAL IDLE SWITCH
• To test these switches, follow the
Testing Switches test procedure
on page 13.
• When you are told to operate
switch, then move throttle linkage.
Vane Air Flow Sensor:
• Slowly open vane “door” from
closed to open by pushing on it
with a pencil or similar object. This
will not harm sensor.
• Depending on hook-up, the dis-
play reading will either increase or
decrease in resistance.
• The display reading should either
start at or end at the approximate
resistance value measured in Step
6.
• Some vane air flow sensors have
an idle switch and an intake air
temperature sensor in addition to a
potentiometer.
• To test idle switch see Testing
Switches on page 13.
• When you are told to operate
switch, then open vane “door”.
Throttle Position Sensor:
• Slowly move throttle linkage
from closed to wide open posi-
tion.
• Depending on hook-up, the dis-
play reading will either increase
or decrease in resistance.
• The display reading should ei-
ther start at or end at the ap-
proximate resistance value
measured in Step 6.
• Some throttle position sensors
have an Idle or Wide Open
Throttle (WOT) switch in addi-
tion to a potentiometer.