oxygen sensor question

[marksr]

Awhile back my 2010 jeep was recalled because the oxygen sensor needed to be reprogrammed in the PCM. I used to get fairly decent gas mileage before the recall - rarely ever less than 20 mpg. Since the recall I struggle to get 19 mpg. I know it isn't a big deal but I'm curious what all the oxygen sensor does and why reprogramming the PCM lost me approximately almost 2 mpg?

[retired wrench]

The o2 sensor sniffs the ex. and tells the computer how to adj. fuel flow.

[Gunguy45]

It could have been running very lean before (most engines run lean nowadays anyway) and caused issues the manufacturer was tired of paying for. So they richen it up a bit, but you use more gas.

Might want to do a search for the full service bulletin/recall and see what it says...

[bicklebok]

Have you tried checking other possible culprits, like tire pressure, air filter, etc?

[marksr]

For the most part I stay on top of tire pressure, filters and such. I hadn't thought about it maybe running too lean..... I was focusing on the decreased mileage Thankfully it's not a vehicle I put a lot of miles on, of course I could say the same thing about my pickup and it only gets 11 mpg

[equinox]

Have you ever confirmed your mileage this time of year in the past? Winter gas, and colder weather does have an impact on mileage also. Just thinking that the drop in mileage may not be necessarily related to your dealer experience.

[marksr]

My mileage has always been fairly consistent. Since I've had the jeep [2yrs] I've never put in less than a full tank and often check the mileage after fill up. I never go by the mileage indicator on the dash as it is consistently 1-3 mpg higher than actual. The only good thing about going to the dealer this time is they finally acknowledged that the clock not keeping time is a defect. Supposedly there is a module fix being worked on..... so maybe by summer the clock can be fixed to keep time. I'd just a soon not have a clock as to have one that looses a minute or so every week