Actron SunPro CP7678 - Mass Air Flow (MAF) Sensors

250V MAX
15A MAX
FUSED
COM
DC
15A
AUTO POWER OFF CP7678
®
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
FLOW
34
Mass Air Flow (MAF) Sensors
This sensor sends a signal to the computer
indicating the amount of air entering the en-
gine. Depending on the sensor design, the
signal may be a dc voltage, low frequency, or
high frequency type. The CP7678 can only
test the
dc voltage and low frequency type
of MAF sensors. The high frequency type
sensors output a frequency that is too high for
the CP7678 to measure. The high frequency
type MAF is a 3-pin sensor used on 1989 and
newer GM vehicles. Refer to vehicle service
manual for the type of MAF sensor your ve-
hicle uses.
Test Procedure (see Fig. 34):
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 MAF sensors.
3. Connect BLACK test lead to good ve-
hicle ground.
4. Connect RED test lead to MAF signal
wire.
• Refer to vehicle service manual for loca-
tion of MAF signal wire.
• You may have to backprobe or pierce
MAF signal wire in order to make con-
nection.
• Refer to vehicle service manual for best
way to connect to MAF signal wire.
5. Turn Ignition Key ON, but do not start
engine!
6. Turn multimeter rotary switch to...
• 20V range for DC type MAF sensors.
• 4 Cylinder TACH position for Low Fre-
quency type MAF sensors.
7. View reading on display.
DC Volts Type Sensor:
• Display reading should be approximately
1V or less depending on MAF sensor
manufacturer.
Low Frequency Type Sensor:
• Display reading should be approximately
330RPM ± 5% for GM Low Frequency
MAF sensors.
• For other Low Frequency type MAF sen-
sors refer to vehicle service manual for
MAF sensor specifications.
• It is O.K. if last two display digits change
slightly while Key is ON.
• Remember to multiply display reading by
10 to get actual RPM.
• To convert RPM to Frequency or vice
versa, use equation below.
Frequency =
RPM
30
{Equation Only Valid for Multimeter in 4
Cylinder TACH Position}
8. Operate Sensor.
• Start engine and let idle.
Black
Ground
Typical GM 1988 & older
Low Frequency type
MAF Sensor
Red
Fig. 34
DC
Only
Frequency
Only