How to Tell if Your O2 Sensor is Bad and How to Fix It

Pretty much every Volkswagen produced since the 80s has sensor for measuring the amount of oxygen in the exhaust. This sensor transmits these signals to the ECM so it can adjust the air/fuel mixture for the engine. This helps your car runs as efficiently as possible while also reducing emissions. Here’s a deeper look at the O2 sensors on your Volkswagen.

Find O2 Sensors for Your Volkswagen Here.

VW oxy sensor

How Does an O2 Sensor Work?

Your Volkswagen’s oxygen sensors are basically monitors with the tip inside the exhaust pipe to detect the oxygen levels in the exhaust. If too much oxygen is running through the exhaust, the system is running too lean — too little and it’s running rich. When the O2 sensor detects this imbalance, it sends signals to the ECM to adjust the air/fuel mix. When an O2 sensor goes bad, the ECM can’t properly adjust for incorrect air/fuel ratios.

Symptoms of a Bad Oxygen Sensor

When there’s a bad O2 sensor in your VW, you can expect the following issues to arise:

Check engine light comes on. This is the easiest way to tell if there’s a bad O2 sensor on your VW — the check engine light will illuminate on your dash. This happens when a trouble code is stored in the ECM and your car is trying to alert you of a problem.

Poor fuel economy. Depending on which one of the O2 sensors is bad, the fuel delivery and combustion systems may become extremely irregular. If too much fuel is sent to your car’s engine, the fuel mileage is going to suffer.

Rough engine idle. When your Volkswagen has a bad oxygen sensor, it will usually idle erratically or roughly.

Engine misfires. Sometimes, a bad O2 sensor will disrupt engine combustion and cause a misfire. These misfires are typically more pronounced at lower idle speeds.

Replacing an O2 Sensor

Once you discover a failed O2 sensor on your VW, you need to replace it right away. Replacement with a genuine Volkswagen oxygen sensor is simple and can be done in your own garage. Here are the steps:

  • Locate the O2 sensor by finding the spark plug looking part ported into your exhaust.
  • Discounted the electrical connection using a flathead and pull the connector away.
  • Unbolt the sensor from the exhaust using an open ended wrench.
  • Reverse these steps to replace the new sensor.
  • After plugging the new sensor in, erase any DTCs from the ECM using a handheld scanner.

Remember to use only OEM quality O2 sensors and related parts to avoid premature wear and failure.