Oxygen Sensor Tech Tips
Knowing which Sensor to Change
Because engine configurations can vary by vehicle, it’s important to correctly identify the specific positions of all your oxygen sensors – so you replace the correct sensor when one of them fails. The post below provides some guidance in understanding which oxygen sensor to change and a few technical tips to assist in a smooth installation process.
Refer to your vehicle service manual to determine your sensor locations. If the manual is not available, here are some guidelines that apply to most vehicles:
Location by Code
- Car makers generally define Bank 1 as the Bank containing Cylinder 1.
- If you don’t know your Cylinder 1 location, ask your auto parts store associate for a cylinder-number- or firing-order diagram for your vehicle. See example at right.
- Sensor 1 is the upstream sensor and Sensor 2 is generally located after the catalyst (downstream)
- On a 3 sensor per bank system, Sensor 2 is located on the catalyst and Sensor 3 is located after the catalyst.
- The front of the engine contains the belt and alternator.
- The transmission is mounted to the rear of the engine.
- Left and right are defined looking from the rear to the front of the engine.
- On rear wheel drive applications, this is the view from the drivers seat.
- Use the bank detail (at left) to determine if you need a forward, rearward, left or right sensor.