Audi Oxygen O2 Sensor Replacement

Is your Audi showing a check engine light with an oxygen sensor code, using more fuel, or idling rough? Learn how to fix it by replacing your vehicle’s Oxygen (O2) Sensor.

This guide covers the upstream oxygen sensors, the ones before the catalytic converter: Bank 1 Sensor 1 and Bank 2 Sensor 1. Also, to change the downstream oxygen sensor for the catalytic converter, you will need to jack up the car and/or use ramps. Also, you must remove the splash shield from underneath the car.

Symptoms

• Check Engine Light is ON
• A decrease in fuel economy
• Engine Hesitation or misfiring
• Rough Idling

What you will need

• Audi Oxygen Sensor
• Oxygen Sensor Tool
• Ratchet Wrench
• Penetrating Oil
• Jack and Jack Stands
  • For downstream sensors. Bank 1 Sensor 2 and Bank 2 Sensor 2 Only.

Procedure

1. Park your Audi, set the parking brake, and open the hood. Do not open the hood while the engine is cooling, as you risk getting burned.
2. Disconnect the negative battery terminal.

3. 

   Locate the oxygen sensor on your Audi. Above, you’ll see the upstream oxygen sensor on an Audi Q5.Location of O2 sensor on Audi A4.

   

4. Disconnect the O2 sensor. Press the connector and pull it away to unplug the connector.

5. Remove the sensor, place the oxygen sensor socket on it, and break it loose. Remove the old Audi oxygen sensor.

6. You may need to spray penetrating oil and allow it to sit for at least ten minutes. Especially on high-mileage Audi cars where the oxygen sensor is stuck.
7. Install the new O2 sensor. Tighten your new Audi oxygen sensor to the new sensor hand tight, then turn an extra 1/2-3/4 turn.
8. Connect the oxygen sensor wire harness by plugging it in. If you use a universal oxygen sensor, you will need to use the diagram with the sensor to find out which wires to splice.
   

The typical cost of changing an Audi oxygen sensor is around $100. This guide will help Audi models such as the A1, A3, A4, A5, A6, A7, Q3, Q5, Q7, and TT.

Check Engine Light Still On

If the check engine light is still on after you replace the O2 sensor, you can use the YOUCANIC UCAN-II Pro to clear the stored codes. This scanner can also read and clear fault codes on the engine and other control modules on supported models.

Upstream or Downstream: Which Sensor Is Bad?

The upstream sensors control the fuel mixture, so a bad one affects how the engine runs and fuel economy. The downstream sensors mainly check the catalytic converter. The fault code tells you which one: Sensor 1 is upstream, Sensor 2 is downstream, and Bank 1 is the side with cylinder 1.

A catalytic converter efficiency code such as P0420 does not always mean a bad sensor. Check for exhaust leaks and misfires before replacing the downstream sensor or the converter.

Frequently Asked Questions

How do I know which Audi O2 sensor to replace?

Read the fault code. Sensor 1 is upstream, before the catalytic converter, and Sensor 2 is downstream. Bank 1 is the side of the engine with cylinder 1.

Can a bad O2 sensor cause poor fuel economy?

Yes. A slow or failed upstream sensor can make the engine run rich, using more fuel and sometimes causing a rough idle.

Do I need to reset anything after replacing an O2 sensor?

Clear the codes, then drive the car so the engine computer can relearn fuel trims and run its sensor tests.

Check these troubleshooting and repair guides for more help on your Audi vehicle.

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