A4 Sedan V6-2.8L (AFC) (1996)
Oxygen Sensor: Testing and Inspection
Checking Oxygen Sensor Heating
OXYGEN SENSOR HEATER, CHECKING:
NOTE:
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Z19 = Oxygen Sensor (02S) heater, bank 1.
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Z28 = Oxygen Sensor (02S) heater, bank 2.
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Disconnect heated oxygen sensor harness connector.
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Switch multimeter (Fluke 83 or equivalent) to 20 volt range and connect between terminals 1 (B+) and 2 (GND).
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Start engine and let idle.
Specified Value: approx. 12 to 14 V.
If the specified value is not obtained:
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Check oxygen sensor heater fuse.
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Check fuel pump relay.
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Check wiring for continuity between terminal 1 and fuse in fuse holder using wiring diagram, if necessary check terminal assignments.
Specified Value: max. 1 Ohms.
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Check wiring for continuity between terminals 2 (O2S heater -Z19-) terminal 10 on ECM connector E.
Specified Value: max. 1 Ohms.
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Check wiring for continuity between terminals 2 (02S heater -Z28-) and terminal 9 on ECM connector E.
Specified Value: max. 1 Ohms.
If the specified value is obtained:
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Switch multimeter (Fluke 83 or equivalent) to measure resistance Ohms and connect between terminals 1 and 2.
Specified Value (room temperature): approx. 2 to 5 Ohms.
NOTE: With small increases in temperature, resistance will increase sharply.
If the specified value is not obtained:
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Replace heated oxygen sensor.