23
Magnetic Pick-Up Coils – Reluctance Sensors
Reluctance sensors are used whenever
the vehicle computer needs to know
speed and position of a rotating object.
Reluctance sensors are commonly used
in ignition systems to determine cam-
shaft and crankshaft position so the ve-
hicle computer knows the optimum time
to fire the ignition coil(s) and turn on the
fuel injectors. This test checks the reluc-
tance sensor for an open or shorted coil.
This test does not check the air gap or
voltage output of the sensor.
Test Procedure (see Fig. 28):
Reluctance
Sensor
Red
Black
1. Insert BLACK test lead into COM
test lead jack.
2. Insert RED test lead into
test lead jack.
Reluctor
Ring
Magnet
3. Connect RED test lead to either
sensor pin.
4. Connect BLACK test lead to re-
maining sensor pin.
5. Turn multimeter rotary switch to
2K
Ω range.
6. View reading on display while flex-
ing sensor wires in several places.
• Typical resistance range is 150 -
1000Ω.
• Refer to vehicle service manual for
your vehicles resistance range.
• As you flex sensor
wires, the display
should remain steady.
7. Test Results
Good Sensor:
Display
reading is within manu-
facturers specification
and remains steady
while sensor wires are
flexed.
Bad Sensor:
Display
reading erratically
changes as sensor wires
are flexed or display
reading is not within
manufacturers specifi-
cation.
Fig. 28
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