Bosch FIX 7677 Mode D'emploi page 28

• Connect BLACK test lead to re-
maining heater pin.
• Turn multimeter rotary switch to
200Ω range.
• View reading on display.
• Compare reading to manufacturer's
specification in vehicle service
manual.
• Remove both test leads from sen-
sor.
6. Connect BLACK test lead to sen-
sor GROUND pin.
• If sensor is 1-wire or 3-wire, then
GROUND is sensor housing.
• If sensor is 2-wire or 4-wire, then
GROUND is in sensor wiring
harness.
• Refer to vehicle service manual for
Oxygen Sensor wiring diagram.
7. Connect RED test lead to sensor
SIGNAL pin.
8. Test Oxygen Sensor.
• Turn multimeter rotary switch to...
– 2V range for Zirconia Type Sen-
sors.
– 200KΩ range for Titania Type
Sensors.
• Light propane torch.
• Firmly grasp sensor with a pair of
locking pliers.
• Thoroughly heat sensor tip as hot
as possible, but not "glowing." Sen-
sor tip must be at 660°F to operate.
• Completely surround sensor tip
with flame to deplete sensor of
oxygen (Rich Condition).
• Multimeter display should read...
– 0.6V or greater for Zirconia Type
Sensors.
– an Ohmic(Resistance) value for
Titania Type Sensors. Reading will
vary with flame temperature.
• While still applying heat to sensor,
move flame such that oxygen can
reach sensor tip (Lean Condition).
• Multimeter display should read...
– 0.4V or less for Zirconia Type
Sensors.
– an overrange condition for Tita-
nia Type Sensors. (See Setting the
Range on page 6.)
9. Repeat Step 8 a few times to verify
results.
10. Extinguish Flame, let sensor cool,
and remove test leads.
11. Test Results.
Good Sensor:
• Heater Circuit resistance is within
manufacturer's specification.
• Oxygen Sensor output signal
changed when exposed to a rich
and lean condition.
Bad Sensor:
• Heater Circuit resistance is not
within manufacturer's specification.
• Oxygen Sensor output signal did
not change when exposed to a rich
and lean condition.
• Oxygen sensor output voltage
takes longer than 3 seconds to
switch from a rich to a lean condi-
tion.
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