Amish Electrician

OK so I am going on a 800 mile trip this weekend...and not to long ago i installed a o/r x pipe with mils..and my check engine light is still on..i reset the code and it come back on it says the driver rear o2 isn't working right. I think that it is messing up my gas mileage to that why i wanted to get it fixed. So i think it is either the mil or the actual sensor itself. so which one should i replace first any suggestions?

devongarver

If it says the drivers rear is acting up, and you are 100% positive the code represents the drivers rear, and all you have is the Mil eliminator, I would assume the Mil is bad. Try swapping the Mil extensions right and left and clear the code to see if it comes back on the other side as a different code. What is the code you were getting BTW?

If it's worth a piece of mind type of thing, I don't think the rear O2 sensors actually control the fuel trim...I think they are nothing more than a "im happy=no CEL" or "im not happy=CEL" type of deal...

Ask CliffyK, he will know.

Amish Electrician

Ok thanks I will try that and idk what the code was i cant remember the numbers but the guy at orielly,s said it was the back driver 02

cliffyk

The rear O2 sensors serve ONLY to monitor the efficiency of the catalytic converters--ONLY. (that's a period)--they have no effect on engine operation; None, Zero, Zilch, Nada.

This is explicitly documented in the shop manuals...

OTOH, aged/sluggish/slow switching front O2 sensors can affect fuel economy--without triggering a DTC. As they get old there output drops and the PCM sees this as a lean mix, so in closed loop mode it will compensate (via the short term fuel trims) by making the mix richer = lousy fuel economy.

The O2 sensor manufacturers will tell you they need to be replaced every 50k, they are actually pretty good for 100k unless you do a lot of short trips and the engine never heats up fully--running rich causes the sensors to fail more rapidly.

If most of your driving is 10 miles or less trips, only a couple times a day, and you have 75k+ miles then replace the front sensors (yourself, not at the dealer).

The increased MPG will pay for it in short order--IF you DIY--if you have to pay someone else to do it they wait 'til you get a DTC...