Any help would go a long way. i just replaced my muffler, and all of a sudden my fuel milage went to crap, I got a check engine light and took it to a local shop to pull the engine codes. Found out the O2 sensor was the problem, but not the solution, because i replaced the O2, disconnected the battery to clear the codes and the check engine light still comes on.

thx pb

 

Pull those codes yet again. Also find out how much current the O2 sensor must have from the computer and check it with a multi-meter you may have a short or a bad connection to the sensor or from the sensor back to the computer or maybe an internally damaged plug. hope this helps.
PS. by the way your local auto-parts store should sell code readers with a guide for reading codes for about $30. Well worth the purchase price considering my dealership charges $84 per hr.

 

did you remove the cats? If so that CAN cause it, there will be a million posts saying that it WONT but it does indeed throw the computer off.

 

I have taken the truck back to the shop to retry the codes and the shop told me that there were no codes stored??, my reply to that was, but the check engine light still comes on. i have two questions ,did they do the retest right (rookie mech.) or did they do the wrong test??? different tests (Keor///Koeo). The first one i thought was the Keor, the second one i think was Koeo, in both the engine was running in the truck with the few different speed run and tire turn, etc. I have the doubt that with the rookie mech that he may have screwed up.

how do I test the new O2 sensor with a multi meter, some where I read that it is damaging or you may get weird reading if you try to test a O2 sensor with a volt meter?????

No cats with the muffler/ tail pipe, flow master delta flow, 2.5 in & out.

Could a leak at the o2 sensor cause any problems?

 

KOEO should be with the Key on, engine off. you said it was running. Have them do it again.