Actron AutoTroubleShooter CP7677 User Manual download pdf (Page 24)

24

Ignition Coil Switching Action

This test checks to see if the negative

terminal of the primary ignition coil is

getting switched ON and OFF via the

ignition module and camshaft / crank-

shaft position sensors. This switching

action is where the RPM or tach signal

originates. This test is primarily used for

a no start condition.

Test Procedure (see Fig. 29):

Fig. 29

Typical

Ignition

Coil

Ground

Black

Red

1. Insert BLACK test lead into COM

test lead jack.

2. Insert RED test lead into

test lead jack.

3. Connect RED test lead to TACH

signal wire.

• If vehicle is DIS (Distributorless

Ignition System), then connect RED

test lead to the TACH signal wire

going from the DIS module to the

vehicle engine computer. (refer to

vehicle service manual for location

of this wire)

• For all vehicles with distributors,

connect RED test lead to negative

side of primary ignition coil. (refer

to vehicle service manual for loca-

tion of ignition coil)

4. Connect BLACK test lead to a good

vehicle ground.

5. Turn multimeter rotary switch

to correct CYLINDER selec-

tion in RPM.

6. View reading on display while

engine is cranking.

• Typical cranking RPM range

is 50-275 RPM depending on

temperature, size of engine,

and battery condition.

• Refer to vehicle service

manual for specific vehicle

cranking RPM range.

7. Test Results.

Good Coil Switching Action:

Display

reading indicated a value consistent

with manufacturers specifications.

Bad Coil Switching Action:

• Display read zero RPM, meaning

the ignition coil is not being

switched ON and OFF.

• Check ignition system for wiring

defects, and test the camshaft and

crankshaft sensors.

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