Measuring fuel injector resistance, Fig. 30 – Actron AutoTroubleShooter CP7677 User Manual

Page 26

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26

Measuring Fuel Injector Resistance

Fuel injectors are similar to solenoids.
They contain a coil that is switched ON
and OFF by the vehicle computer. This
test measures the resistance of this coil
to make sure it is not an open circuit.
Shorted coils can also be detected if the
specific manufacturer resistance of the
fuel injector is known.

Test Procedure (see Fig. 30):

Fig. 30

Typical Fuel

Injector

Black

Red

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. Turn multimeter rotary switch to

200

range.

Touch RED and BLACK multimeter
leads together and view reading on
display.

Display should read typically 0.2 -
1.5

.

If display reading was greater than
1.5

, check both ends of test leads

for bad connections. If bad connec-
tions are found, replace test leads.

4. Disconnect wiring harness from

fuel injector - Refer to vehicle ser-
vice manual for procedure.

5. Connect RED and BLACK test

leads across fuel injector pins.

Make sure you connect test leads
across fuel injector and not the wir-
ing harness.

6. Turn multimeter rotary switch to

desired OHM range.

If the approximate resistance is
unknown, start at the largest
OHM range and decrease to the
appropriate range as required.
(see Setting the Range on page
6)

7. View reading on display -

Note range setting for cor-
rect units.

• If display reading is 10

or

less, subtract test lead resis-
tance found in Step 3 from
above reading.

• Compare reading to manu-

facturers specifications for
fuel injector coil resistance.

• This information is found in

vehicle service manual.

8. Test Results

Good Fuel Injector resistance: Re-
sistance of fuel injector coil is within
manufacturers specifications.

Bad Fuel Injector resistance: Resis-
tance of fuel injector coil is not within
manufacturers specifications.

NOTE: If resistance of fuel injector
coil is within manufacturers specifi-
cations, the fuel injector could still
be defective. It is possible that the
fuel injector is clogged or dirty and
that is causing your driveability prob-
lem.

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