How to Install an Oxygen Sensor in a 2000 Audi A4
- 1). Park the vehicle, set the parking brake, shut off the engine and open the hood. Wait for the engine and exhaust system to cool completely, before proceeding, to avoid burns.
- 2). Locate the sensors; there are two of them. The upstream is threaded into the exhaust manifold, which is in the lower engine area on the passenger's side, below the exhaust pipe flange and before the catalytic converter. The downstream sensor is threaded into the exhaust pipe after the catalytic converter.
- 3). Spray penetrating lubricant at the base of each sensor and let it set in for 30 minutes before proceeding. This will help loosen the sensor for easier removal.
- 4). Unplug the sensor wire on the upper (upstream) sensor from the vehicle's connector. Back out the sensor by rotating it counterclockwise with a sensor socket and ratchet. Insert the new sensor into the hole and tighten it with the sensor socket, using a clockwise rotation. Connect the sensor wire to the connector on the vehicle.
- 5). Repeat Step 4 for the lower (downstream) sensor.
