Actron CP7677 Operations Instructions download pdf (Page 32)

32

12.View reading on display.

DC Volts Type Sensor:

• Verify hand held vacuum pump is

at 0 in. of vacuum.

• Display reading should be approxi-

mately 3V or 5V depending on

MAP sensor manufacturer.

Frequency Type Sensor:

• Verify hand held vacuum pump is

at 0 in. of vacuum.

• Display reading should be approxi-

mately 4770RPM ± 5% for Ford

MAP sensors only.

• For other frequency type MAP sen-

sors refer to vehicle service manual

for MAP sensor specifications.

• It is O.K. if last two display digits

change

slightly while vacuum is

held constant.

• 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 RPM Position)

13.Operate Sensor.

• Slowly apply vacuum to MAP sen-

sor - Never exceed 20 in. of vacuum

because damage to MAP sensor

may result.

• Display reading should decrease

in

voltage or RPM as vacuum to

MAP sensor is increased.

• Refer to vehicle service manual

for charts relating voltage and fre-

quency drop to increasing engine

vacuum.

• Use equation above for Frequency

and RPM conversions.

14.Test Results.

Good Sensor:

• Sensor output voltage or

frequency(RPM) are within manu-

facturers specifications at 0 in. of

vacuum.

• Sensor output voltage or frequency

(RPM) decrease with increasing

vacuum.

Bad Sensor:

• Sensor output voltage or frequency

(RPM) are not within manufactur-

ers specifications at 0 in. of

vacuum.

• Sensor output voltage or frequency

(RPM) do not change with increas-

ing vacuum.

Mass Air Flow (MAF)

Sensors

This sensor sends a signal to the com-

puter indicating the amount of air enter-

ing the engine. Depending on the sen-

sor design, the signal may be a dc volt-

age, low frequency, or high frequency

type. The CP7677 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 CP7677 to measure. The

high frequency type MAF is a 3-pin sen-

sor used on 1989 and newer GM ve-

hicles. Refer to vehicle service manual

for the type of MAF sensor your vehicle

uses.

Test Procedure (see Fig. 35):

1. Insert BLACK test lead into COM

test lead jack.

2. Insert RED test lead into

test lead jack.

3. Connect BLACK test lead to good

vehicle ground.

4. Connect RED test lead to MAF

signal wire.

• Refer to vehicle service manual for

location of MAF signal wire.

• You may have to backprobe or

pierce MAF signal wire in order to

make connection.

• 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...

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