help again with TJ o2 sensor??

Question

ok, replaced o2 sensor after checking codes, got 12 & 21 had to disconnect battery to clear code 21 even after replacing o2 sensor. with in 24 hours the check engine light pops back on. damn same codes again

12 & 21. so we have a new o2 sensor in place? so disconnect battery again just on a whim and code 21 is cleared??

any Ideas?? bad battery ?? charge indicator shows 14volts if gauge is close. no problem with dim light---- no problem with starting- only problem I have is check engine light comes on?

could voltage regulator be going out ??

in the dark with no flashlight - ya gotta lead me by hand!! thanks

Jerry Bransford · Accepted Answer

Which 02 sensor did you replace?  There are at least two 02 sensors on earlyTJs and from what I hear and read, four 02 sensors on the latest TJs.Jerry

casca · Answer

only one that I was aware of was one down on exhaust before cat. converter.did not see any others mentioned in any manuals or at auto parts stores ?thanks

David C. Moller · Answer

What Jerry said... the 21 can indicate either the upstream or thedownstream O2 sensor.Dave

L.W.(ßill) · Answer

God Bless America, ßill O|||||||Omailto:     casca wrote:

casca · Answer

tell me more , where can I find more info & or picture??

casca · Answer

well in for a penny in for a pound ?? guess will have to change rear sensor"I thought" ( that's where the problem usually starts)that there was only one-- at one end or the other !! so will go check andswitch the other. At 79000 miles probably about due??just can't figure out why code clears temporary after battery disconnectedor does it just take awhile for it to get a good reading??think I can get away driving it for a few days , until I can get under it??thanx

David C. Moller · Answer

I believe they (upstream/downstream) are interchangeable (may be wrongthough). I'd probably replace both for the heck of it, but if youwanted to, you could probably try the new one in the other location,and put an 'old' one back where you had the new one.Disconnecting the battery will clear all codes (except batterydisconnect code), so it makes sense that everything is fine until itsenses the O2 malfunction again IMO.From what I know, you're fine driving for a while if it's an O2 sensorfailure. It's strictly an emissions thing... won't hurt the vehicle.Dave

Peter Parker · Answer

Only that you will get $hitty gas mileage and will be running inefficient. I would suspect a bad wire at one of the O2 sensor connectors. Intermittant. Pull on the wires or use a volt meter to determine a proper connection.

Carlo Jr. · Answer

I say again.............find someone with a scanner that has data stream -that way you can determine if it is a sensor or if it is what it issensing..............

help again with TJ o2 sensor??

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