Golf III L4-2.0L (ABA) (1995)
Oxygen Sensor: Testing and Inspection
Without VAG
HEATED OXYGEN SENSOR CHECKING
NOTE: Oxygen Sensor heating is controlled by the Heated Oxygen Sensor (HO2S) Control Module, located in position # 13 of the fuse/relay panel.
PRE-TEST REQUIREMENTS
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Fuse 18 OK
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Exhaust system not leaking
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Voltage supply to Motronic Engine Control Module (ECM) OK
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Engine at normal operating temperature
ELECTRICAL TESTING
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Disconnect harness connector to oxygen sensor heater.
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START engine and let idle.
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Connect LED test light between terminals of oxygen sensor heater harness connector.
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LED should light
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IF NOT check fuse and wiring to Heated Oxygen Sensor Control Module.
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Fold back rubber boot at oxygen sensor signal lead, do not separate connectors.
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Connect voltmeter between exposed sensor lead and ground.
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Voltmeter should oscillate between 0.1 and 0.9 VDC
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If reading is fixed at 0.4 - 0.6 VDC, check for open circuit between sensor and ECM.
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If reading is too low, check for grounded signal wire, intake leak, or heater element operation.
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If reading is too high, check for signal lead short to other wiring.
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If wiring is OK, replace sensor and recheck.