90CS Quattro V6-2.8L (AAH) (1994)
2-Pin Connector
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Connect multimeter (Fluke 83 or equivalent) between connector terminals 1, Ground (GND), and 2, positive (8+).
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Start engine and let idle.
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Specified value: approx. 12-14 volts
If specified values are not obtained:
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Check HO2S circuit breaker -S73- (brown holder in electronics box, passenger side footwell).
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Check continuity in wiring from connector terminal 2 to circuit breaker using wiring diagram.
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Specified reading: maximum 0.5 ohms
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Check continuity in wiring from connector terminal 1 to GND.
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Specified reading: maximum 0.5 ohms
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Check fuel pump relay.
If the specified reading is obtained:
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Connect additional test harness VAG 1315 A/1 into 2-pin HO2S connector.
This series connection allows actual current flow measurement
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Switch multimeter to 10 amp (DC) measuring range and connect (connect test harness to 10 amp connector).
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Run engine.
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Specified reading: 0.5-3.0 amps (Current decreases as sensor temperature increases).
If specified reading is not obtained:
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Replace oxygen sensor.
Checking Oxygen Sensor control
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Disconnect harness connector for oxygen sensor signal wire.
1C - Right bank
4A - Left bank
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Connect multimeter between oxygen sensor signal wire and GND.
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Specified value: infinite ohms (no continuity)
If specified values are not obtained:
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Replace HO2S.
If specified value is obtained:
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Switch multimeter to 2.0 volt measuring range and connect between signal wire connector of wiring harness to ECM and GND.
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Switch ignition on.
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Specified value: 400 +/- 50 mV
If specified values are not obtained, check wiring to ECM:
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Switch ignition OFF.
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Connect VAG 1598 test box on ECM wiring harness using VAG 1598/11 adapter harness. See: Testing and Inspection/Scan Tool Testing and
Procedures/Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1598/31 Test Box
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Adapter harness for ECM is not connected.
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Check for continuity between H02S -G39- signal wire and test box socket 50.
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Specified value: max. 1 (ohm)