If you hear a tone the fuse is good. If there is no
tone the fuse is blown and needs to be replaced.
Solenoids/Relays
This test checks the solenoid or relay for a broken
internal coil. Typically a resistance of 200Ω or less is
present in a good solinoid/relay. If a high resistance is
detected the unit has break in the coil and is bad.
1. Insert BLACK test lead into COM test lead jack.
2. Insert RED test lead into test lead jack.
3. Turn the meters range selector to 200Ω function.
If the meter over ranges, turn the meters range
selector to next higher range.
4. Add the alligator clips and connect BLACK
clip to one side of coil.
5. Connect RED clip to other side of coil.
View results on display. If the solenoid/relay coil
resistances is 200Ω or less, the unit should be good.
Refer to vehicle service manual for your vehicles
resistance range.
• A good Solenoid/Relay Coil displays results within
manufacturer’s specification.
• A bad Solenoid/Relay Coil displays results not
within manufacturer’s specifications. If the display
reads over range, that indicating an open circuit or
defective Solenoid/Relay
Distributor Cap/Rotor Resistance
This test checks for open circuits or high
resistance in the distributor cap and rotor if your
vehicle is so equipped.
1. Insert BLACK test lead into COM test lead jack.
2. Insert RED test lead into test lead jack.
3. Turn meters range selector to 200Ω range.
4. For the distributor cap test connect the test leads
to opposite ends of the distributor cap. One into the
top center of the cap (coil wire position). The other
on lead touches the inside center of the cap, view
the displayed results. General resistance should be
5K – 10K. Refer to vehicle service manual for your
vehicles resistance range.
5. For the rotor test connect the test leads to opposite
ends of the rotor. One to the top metal contact, and
the other to the extended metal finger contact.
General resistance should be 0.1Ω or less. Refer
to vehicle service manual for your vehicles
resistance range.
Variable Reluctance Sensor
A variable reluctance sensor is a transducer that,
detects the change in presence or proximity of
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IGNITION SYSTEM TESTS
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ferrous objects. Reluctance sensor are used
whenever the vehicle’s ECU needs to know speed
and/or the position of a rotating object. In ignition
systems, it’s used to determine camshaft and
crankshaft position. This tells the vehicle ECU when
to fire the ignition coil and turn on the fuel injectors.
Speed sensors are another type of reluctance
sensor used in transmissions to measure the
rotational speed of shafts. These sensors help the
ECU to determine when to shift from one gear to
the next.
1. Insert BLACK test lead into COM test lead jack.
2. Insert RED test lead into test lead jack.
3. Add the alligator clips and connect the RED
clip to either pin on the Variable Reluctance Sensor.
4. Connect the BLACK clip to the remaining pin.
5. Turn the meters range selector to largest 2KΩ
range. View and record the reading on the display.
6. Now watch the meter while flexing the sensor
wires from the harness connection to the sensor.
Common resistance range is 100 to 1KΩ, refer to
your service manual for resistance range.
• A good sensors display reading will fall within
manufacturer’s specification. There is no erratic
changes in the display readings, results are steady
while sensor wires are flexed.
• A bad sensors display reading changes when the
wiring is flexed, or the reading is not within
manufacturers specifications.
Crankshaft Timing Sensor
The Crankshaft timing sensor is typically located in
the front of the crankshaft to trigger the ignition
system. This sensor consists of a single Hall Effect
magnetic switch activated by 3 vanes on the
crankshaft damper and pulley assembly. This
sensor sends a signal that feeds timing and RPM
information to the DIS and EPU.
To test if it your crankshaft position sensor is working
properly, you need to test for a voltage output.
1. Insert BLACK test lead into COM test lead jack.
2. Insert RED test lead into test lead jack.
For this test you’ll need to back probe or add jumper
leads from the two pin in the harness.
3. Turn the meters range selector to 2V AC range.
4. Crank the engine, view and record the reading
displayed. A normal reading would be at or near .2
volts. Refer to vehicles service manual for
recommended voltage outputs.
Some reference manuals states a resistance
value, if so you can check the sensor without
cranking the engine.
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