A4 Sedan V6-2.8L (AFC) (1996)
Oxygen Sensor: Testing and Inspection
HO2S Before Three Way Catalytic Converter (TWC), Checking
Heated oxygen sensor, checking
NOTE:
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G39 = Heated Oxygen Sensor (HO2S), bank 1
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G108 = Heated Oxygen Sensor (HO2S) 2, bank 2
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Functional check of HO2S -G39- or -G108-.
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Disconnect Heated Oxygen Sensors (HO2S) -G39- or -G108- harness connector (component locations, refer to "Component Overview - II" See:
Powertrain Management/Fuel Delivery and Air Induction/Locations ).
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Switch multimeter (Fluke 83 or equivalent) to measure resistance (ohms) and check for continuity between terminal 4 oxygen sensor signal wire
(measured at oxygen sensor connector) and engine Ground (GND).
If continuity is not obtained:
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Replace heated oxygen sensor.
If continuity obtained:
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Switch multimeter to 2 volt range and connect between terminal 4 on harness connector and engine Ground (GND).
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Switch ignition ON.
Specified value: 400 ± 50 mV
If the specified value is not obtained, check wiring to ECM as follows:
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Switch ignition OFF.
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Connect VAG 1598/19 test box to ECM harness connector.
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Check wiring for continuity between terminal 4 (HO2S -G39-) and terminal 20 on ECM connector A.
Specified value: max. 1 ohms
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Check wiring for continuity between terminal 4 (HO2S 2 -G108-) and terminal 21 on ECM connector A.
Specified value: max. 1 ohms
If the specified value is not obtained: