What is the 2003 VW Passat o2 sensor location?

On Your 2003 Volkswagen Passat, there are two O2 sensors. You'll find the front one located about a foot upstream of the inlet pipe for the catalytic converter. The rear sensor is located about the same distance downstream of the converter. The distance can vary slightly depending which trim level You've got. A budget friendly replacement option is going to be the Walker Exact Fit Oxygen Sensor, part #350-34601 from AutoZone, which runs at around $50. Replacing the sensor is as simple as unscrewing the old one and disconnecting the wire harness pigtail from it, hooking that up to the new part, and screwing it in. You may need to manually clear any diagnostic trouble codes, or the check engine light manually, if it was illuminated.