Master O2 Sensor Troubleshooting: Upstream vs. Downstream Made Simple
In this Tech Tip Short, Erik Screeden, technical and multimedia content director for Motor Age, dives into one of the most common yet confusing diagnostic issues — oxygen sensor troubleshooting. Many technicians face challenges when interpreting OBD-II codes, especially when it comes to identifying the correct O2 sensor bank location.
Screeden explains how to properly decode terms like bank 1 and bank 2, as well as the difference between upstream and downstream O2 sensors. Using the example of a P0157 diagnostic code, he shows how a downstream sensor on bank 2 might be misidentified if you don’t confirm where cylinder one is located. The video also highlights how catalytic converter efficiency monitoring plays a role in interpreting sensor signals. By following these steps, you can save time, avoid mistakes, and make the right replacement the first time. With Walker Products O2 sensors, you’ll get OE-quality performance every time. Watch the full short to learn more and sharpen your diagnostic skills. Learn more about Walker O2 sensors here.
About the Author
Erik Screeden
Technical and Multimedia Content Director
Erik Screeden is the Technical and Multimedia Content Director for the Vehicle Repair Group. He has been in the automotive industry for over 24 years. During that time, Screeden was a technician. He started out at a Ford dealership and continued to several independent repair facilities as well as spent time in the specialty aftermarket where he had the opportunity to work at a GM-specific performance shop. After his time as a technician came to an end, Screeden transitioned into a role providing scan diagnostic and J2534 tool support. He was then able to parlay his experience as a technician and a support specialist and use that in several technical sales roles.