2005 Jeep Wrangler Rural Carrier Edition (RHD)

I am a Rural Letter Carrier with a 2005 Jeep Wrangler right hand drive…43K miles My “check engine” light came on about 3 weeks ago. (I drive approximately 40 miles a day on my route.) I took it to a diagnostics center to be scanned. They said it was a “lean condition or a downstream oxygen sensor malfunction”??? and they could not clear it as Chrysler/Jeep had put out a service bulletin on it clear it. They said it would cost upwards of $100+ to clear it. This is money we do not have as the fuel prices, etc have made it so we almost pay the Post Office to deliver the mail.



My husband disconnected the battery contact for about 5 minutes and the light went off…it has not come back on and it has been over a week.



1st: what is a lean condition or a downstream oxygen sensor malfunction?



2nd: Does it affect my mileage? I have noticed in the last week or so that I’m using a lot more gas. Or so it seems.



3rd: Would the size of my tires affect the mileage? I am using studded snow tires.