32
switch, then open vane
“door”.
• To test intake air tempera-
ture sensor see Temperature
Type Sensors on page 29.
EGR Valve Position
• Remove vacuum hose from
EGR valve.
• Connect hand vacuum pump
to EGR valve.
• Gradually apply vacuum to
s l o w l y o p e n v a l v e .
(Typically, 5 to 10 in. of
vacuum fully opens valve.)
• Depending on hook-up, the
display reading will
either
increase
or
decrease in re-
sistance.
• The display reading should
either
start at
or
end at the
approximate resistance
value measured in Step 6.
9. Test Results.
Good Sensor:
D i s p l a y
reading gradually i ncreases
or
decreases in resistance as
sensor is opened and closed.
Bad Sensor:
There is no
change in resistance as sen-
sor is opened or closed.
Manifold Absolute
Pressure (MAP) and
Barometric Pressure
(BARO) Sensors
This sensor sends a signal to the com-
puter indicating atmospheric pressure
and/or engine vacuum. Depending on
the type of MAP sensor, the signal may
be a dc voltage or a frequency. GM,
Chrysler, Honda and Toyota use a dc
voltage MAP sensor, while Ford uses a
frequency type. For other manufactur-
ers refer to vehicle service manual for
type of MAP sensor used.
Test Procedure (see Fig. 34):
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 and
vacuum line from MAP sensor.
4. Connect jumper wire between Pin
A on wiring harness and sensor.
5. Connect another jumper wire be-
tween Pin C on wiring harness
and sensor.
6. Connect RED test lead to sensor
Pin B.
7. Connect BLACK test lead to good
vehicle ground.
8. Make sure test leads and jumper
wires are not touching each other.
9. Connect a hand held vacuum
pump to vacuum port on MAP sen-
sor.
10. Turn Ignition Key ON, but do not
start engine!
11. Turn multimeter rotary switch to...
• 20V range for DC type MAP
sensors.
• 4 Cylinder RPM position for Fre-
quency type MAP sensors.
Fig. 34
Ground
Red
Black
Typical
GM
MAP
Sensor
To
Computer
DC
Only
Frequency
Only
600
600
