brought to you by 1a auto calm your source for quality replacement parts and the best service on the Internet hi I'm Mike from 1a auto I hope this how-to video helps you out and next time you need parts for your vehicle think of 1a auto calm thanks in this video we're going to show you how to replace an o2 sensor on this 2003 Chevy Blazer s10 with the 4.3 liter v6 and it's the same part and process in a large variety of GM vehicles we're going to start off by showing you we plugged in an obd2 sensor to find out what the check engine light was and it gave us these error codes 154 155 which ended up being a upstream o2 sensor so if you come under the vehicle here you'll see this is your downstream o2 sensor and then up front here this is your bank 1 upstream o to sensor and this over here is your bank to upstream o2 sensor this one is the one that has the issue you just want to start off by pulling out the blue pin on the harness for the o2 sensor and then disconnecting that harness and the harness is clipped to the vehicle you just want to pull that out and you can use a pair of pliers to help you remove it you'll notice Don gets a little impatient and just cuts it you can do that too because you're going to have a new one anyways you can buy a socket specifically for the o2 sensors and you can buy that at 1a auto comm for this particular oxygen sensor just using a 7/8 wrench is a better solution but for the other two sensors on this vehicle the socket might be a better solution now using a wrench you just want to loosen up and remove your o2 sensor and we'll just fast forward as dawn loosens this up the rest of the way you the old part in the back the new o2 sensor from 1a auto in the front you can see they're identical the new one just has a clip that hasn't been cut you just want to feed your new o2 sensor up into position and just twist it in it's easier to just twist it in by hand and then once you get it in most of the way tighten it up the rest of the way with the wrench and now just reconnect your harness and slide that blue pin back into place and reclip your harness to the vehicle and you're all set we hope this helps you out brought to you by WWE 1a auto calm your source for quality replacement parts and the best service on the internet please feel free to call us toll-free 888 eight four four three three nine three we're the company that's here for you on the internet and in person