How to Replace an Oxygen Sensor Saturday Mechanic

It’s always the upstream sensor (“Bank 1, Sensor 1”) that the powertrain management system pays attention to in order to fine-tune the proper 14.7:1 air/fuel ratio (aka lambda). Lambda is the Greek character used to designate that perfect stoichiometric ratio. And although the modern oxygen sensor has a 100,000-mile life expectancy, when it gets old a..