Actron AutoTroubleShooter CP7677 - Manual (Page 26)

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
Ω
range.
Touch RED and BLACK multimeter
leads together and view reading on
display.
Display should read typically 0.2 -
1.5
Ω
.
If display reading was greater than
1.5
Ω
, 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
Ω
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.