Genuine Audi 90 Oxygen Sensor

Audi 90 Oxygen Sensor Parts and Q&A

• Oxygen Sensor
  034-906-265-F
  Q: How to check the Idle Control Valve and Oxygen Sensor on Audi 90?

  A:

  For idle speed boost with engine code JN, connect an exhaust gas analyser to the CO measuring pipe when the engine is at normal operating temperature. Start the engine and let it idle for at least two minutes, then note the CO content and clamp hose 2; the CO content should briefly increase and then decrease. If it does not, disconnect the lambda probe wires and hold the green wire to earth for about twenty seconds; if the CO content changes, the lambda probe is faulty. For lambda control with engine code PS, follow the specified procedures. To check cold acceleration enrichment, connect a multimeter to the differential pressure regulator, disconnect the plug from the lower temperature sender, and remove the air intake elbow from the airflow meter. Turn on the ignition and ensure the control current is between 80 to 100 mA, then quickly lift the airflow meter plate to see the control current rise above 100 mA. For re-start and warm-up enrichment, disconnect and earth the HT lead from the ignition coil, connect a multimeter to the differential pressure regulator, and disconnect the plug from the lower temperature sender. Operate the starter for about two seconds while keeping the ignition on; the control current should reach 120 mA for 30 to 60 seconds, then drop to 80 to 100 mA within 20 to 50 seconds. For the cold start valve and thermotime switch, follow the specified procedures, as well as for the auxiliary air valve and basic throttle valve setting.
• Oxygen Sensor
  078-906-265-B
  Q: What is the role of the Oxygen Sensor and Throttle Position Sensor in the KE-Motronic system regarding fault memory and component testing on Audi 90?

  A:

  The KE-Motronic system features a fault memory that encompasses both the fuel injection and ignition systems. To check lambda control, connect a digital multimeter to the differential pressure regulator, let the engine idle for two minutes at normal operating temperature, note the control current, then disconnect hose 1 to observe an increase in control current. If there is no change, disconnect the lambda probe wires and ground the green wire for about twenty seconds; a change in control current indicates a faulty lambda probe. For start enrichment, connect a digital multimeter to the differential pressure regulator, disconnect the ignition coil power stage wiring, remove fuse 13, operate the starter, and ensure the control current drops to 35 to 45 A for a maximum of three seconds before returning to zero. To test overrun cut-off, connect a digital multimeter to the differential pressure regulator, switch on the ignition, note the control current, start the engine and increase the speed to over 3000 rpm, then quickly close the throttle to check for a brief negative indication in control current. For the cold start valve, disconnect the ignition coil power stage wiring, disconnect the temperature sender wiring and connect a 15 kilohm resistance in series, remove the cold start valve and check for an even 'cone' spray pattern for about eight seconds when the starter is operated, ensure the valve remains dry for at least a minute, and finally, check the valve terminals with an ohmmeter for a reading of 10 ohms. Special test leads are necessary for testing throttle valve switches, and this task is recommended to be performed by an Audi dealer.