EGR Valve Position
• Remove vacuum hose from EGR valve.
• Connect hand vacuum pump to EGR
valve.
• Gradually apply vacuum to slowly open
valve. (Typically, 5 to 10 in. of vacuum
fully opens valve.)
• Depending on hook-up, the display read-
ing 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.
9. Test Results.
Good Sensor:
Display reading gradually
increases or decreases in resistance as
sensor is opened and closed.
Bad Sensor:
There is no change in resis-
tance as sensor is opened or closed.
32
Test Procedure (see Fig. 33):
1. Insert BLACK test lead into COM test
lead jack.
2. Insert RED test lead into..
•
test lead jack for DC type or
low frequency type MAP sensors.
Manifold Absolute Pressure
(MAP) and Barometric
Pressure (BARO) Sensors
This sensor sends a signal to the computer
indicating atmospheric pressure and/or en-
gine 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.
Fig. 33
Ground
Red
Black
Typical
GM
MAP
Sensor
To
Computer
250V MAX
15A MAX
FUSED
COM
DC
15A
OFF
200
20
2
DC V
200
m
20M
200
K
20K
2K
200
8CYL
6CYL
TACH
X10
5CYL
4CYL
8CYL
6CYL
5CYL
4CYL
DWELL
DUTY
CYCLE
%
OHMS
°
15
A
C
B
A
30
25
20
15
5
0
10
V A C U U M P U M P
DC
Only
Frequency
Only
