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Home >> Audi >> 1991 >> 100 Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Engine Sensors & Switches 2.3L >> Oxygen (O2) Sensor
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Oxygen (O2) Sensor

  1. Disconnect differential pressure regulator connector from side of regulator. Using Adapter (1315 A/1), connect Multimeter (US 1119) to differential pressure regulator and to the connector removed from regulator.
  2. Set multimeter to 200-mA DC scale. Disconnect O2 sensor connector. Start engine and let idle. Note reading on multimeter. Ground male end of O2 sensor connector.
  3. Observe multimeter. Current should increase from 9 mA to 11 mA after 15 seconds. If multimeter reading is not as specified, check wiring between FICU and O2 sensor harness connector.
  4. If wiring is okay, replace FICU. Connect O2 sensor and start engine. Raise engine speed to about 3000 RPM for a few seconds.
  5. Differential pressure regulator current must return to original mA value, and fluctuate approximately 1-3 mA in the -10 10 mA range. If current does not return to original mA value or does not fluctuate, replace O2 sensor.
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