S6 Wagon L5-2226cc 2.22L DOHC Turbo (AAN) (1995)
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Heated Oxygen Sensor: Testing and Inspection
Checking Control Function With Scan Tool
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Select "Reading measuring value block" function 08 on VAG 1551 Scan Tool (ST) and input display group 01. Refer to On-Board
Diagnostics. See: Testing and Inspection
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Observe display value in channel 3.
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Must be: 0.96 - 1.04.
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Display must not remain at 1.0 (average value); value must fluctuate.
If specified value is NOT obtained:
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Check for the following malfunctions:
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Fuel system pressure too high or too low.
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Leak in intake air system between Mass Air Flow (MAF) sensor.
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Leak in exhaust system between engine and Heated Oxygen Sensor (HO2S) probe.
Note:
A display value OVER 1.04 indicates that the HO2S has detected a lean condition, and to compensate, has enriched the control system.
The following can produce a lean condition:
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Low fuel system pressure.
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Auxiliary air intake in intake area.
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Air leak forward of HO2S.
A display value UNDER 0.96 indicates that the HO2S sensor has detected enrichment and to compensate, has created a lean condition.
The following can produce enrichment:
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Excessive fuel system pressure.
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Air leak in system past turbocharger.
A display that remains fixed at the average value 1.00 indicates the following:
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Electrical malfunction in HO2S control system.
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Open circuit.
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Short circuit.
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Sensor probe malfunctioning.
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Control module malfunctioning.
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Insufficient heating of HO2S probe.
