[myself]

'96 zj I6 - went to get an inspection. the scary lady at the inspection place said my junk wouldn't pass with the check engine light on. :v8:

it's been on and off for the past 6 months... i've kinda ignored it.

anyway, here's the codes i just pulled - 12, 21 and 51. i found this site... http://minimopar.knizefamily.net/fault/ and tried to figure them out based on the info there but i guess i'm stupid( not saying i'm not ).

based on the info there it looks like i need to replace my oxygen sensor... would that be a fair assessment? basically i just want the freakin' light off so it'll pass inspection... any suggestions besides just disconnecting the light?( i already asked and it still won't pass if i did that )

:thumbsup:

 

[Jim311]

I'm pulling these from a Haynes manual.



12- Battery power to PCM was disconnected.

-Basically your battery has recently been disconnected. Once the engine has been turned on and off like 50 times or something like that it will go away.


21- Oxygen sensor input voltage maintained above the normal operating range.

- Time to get a new O2 sensor.


51- A lean air/fuel mixture has been indicated by an abnormally rich correction factor.

- Basically your engine thinks it's still cold and is running richer than it should be. More fuel than necessary. I think you might foul your plugs or experience detonation eventually.







Go to your nearest parts store and pick up a Bosche sensor. Make sure it's got the round plug. Unscrew your O2 sensor from in front of the cat and replace it with the new one. I think you can get the part for about 80 bucks. If you're set on having your engine run rich and waste lots of gas then don't replace it. You could even buy one, use it for inspection, and then return it shortly after with nobody the wiser. Just tell them it didn't fit and you got one elsewhere. Hope this helped.

 

[JordoVR]

Hey that actually helps me a decent amount. I had the fault codes of 12 and 21 and knew that it may have something to do with my O2 sensor since the jeep actually will stutter occaisonally when accelerating.

So you recommend the Bosch sensor? Do you know a cheap place to get them or any other sensor?

Is the installation very difficult? I'm a decent mechanic but I just got my GC so I am not too familiar with it yet. I was thinking about grabbing a Haynes manual as well. Anyway... After searching through the forum I noticed some people said they had problems getting up under the tranny where the connector for the upstream O2 sensor is located. And also I have a 97 so I have two sensors right... and upstream and downstream? And the upstream is the one I want to replace?

Thanks for any info!
_________________________
'97 ZJ, 318 V8, 31" AllTerrains

 

[Jim311]

Honestly, I'd replace both of the O2 sensors if it were me. It's an EXTREMELY easy thing to change. The parts might cost you a bit more but you'll probably see a difference in fuel economy. I've seen some people say you should buy a Mopar O2 sensor but I don't really see any difference. My Bosche was like 70 bucks or something. Mine wasn't hard to change at all.. it's nowhere near my transmission or anything that would obstruct it too badly. Just unscrew the old one, put in the new one, and it's done. Simple fix and you'll get better performance and gas mileage to boot. I believe the Haynes said that code is for the upstream, so if you just want to replace that one I'm sure you could. The upstream one controls rich/lean settings, and the downstream one just monitors the effectiveness of your catalytic convertor.

 

[myself]

I'm pulling these from a Haynes manual.



12- Battery power to PCM was disconnected.

-Basically your battery has recently been disconnected. Once the engine has been turned on and off like 50 times or something like that it will go away.


21- Oxygen sensor input voltage maintained above the normal operating range.

- Time to get a new O2 sensor.


51- A lean air/fuel mixture has been indicated by an abnormally rich correction factor.

- Basically your engine thinks it's still cold and is running richer than it should be. More fuel than necessary. I think you might foul your plugs or experience detonation eventually.







Go to your nearest parts store and pick up a Bosche sensor. Make sure it's got the round plug. Unscrew your O2 sensor from in front of the cat and replace it with the new one. I think you can get the part for about 80 bucks. If you're set on having your engine run rich and waste lots of gas then don't replace it. You could even buy one, use it for inspection, and then return it shortly after with nobody the wiser. Just tell them it didn't fit and you got one elsewhere. Hope this helped.

:thumbsup: you're the man, jim.

so if i grab a new o2 sensor it seems like that would take care of code 21 and 51... right? and if i install it do those codes clear after awhile or will i need them cleared with a scan tool?

 

[JordoVR]

Were you able to change the 02 sensor without jacking up your rig?

 

[Jim311]

I'm pulling these from a Haynes manual.



12- Battery power to PCM was disconnected.

-Basically your battery has recently been disconnected. Once the engine has been turned on and off like 50 times or something like that it will go away.


21- Oxygen sensor input voltage maintained above the normal operating range.

- Time to get a new O2 sensor.


51- A lean air/fuel mixture has been indicated by an abnormally rich correction factor.

- Basically your engine thinks it's still cold and is running richer than it should be. More fuel than necessary. I think you might foul your plugs or experience detonation eventually.







Go to your nearest parts store and pick up a Bosche sensor. Make sure it's got the round plug. Unscrew your O2 sensor from in front of the cat and replace it with the new one. I think you can get the part for about 80 bucks. If you're set on having your engine run rich and waste lots of gas then don't replace it. You could even buy one, use it for inspection, and then return it shortly after with nobody the wiser. Just tell them it didn't fit and you got one elsewhere. Hope this helped.

:thumbsup: you're the man, jim.

so if i grab a new o2 sensor it seems like that would take care of code 21 and 51... right? and if i install it do those codes clear after awhile or will i need them cleared with a scan tool?

I think the codes should disappear eventually. I'm not sure if they'll do it instantaneously, however. Might take a few cycles but I don't think you'll need a scan tool to reset it or anything. Worst come to worst you could disconnect the battery cable. Although doing so will cause you to throw a code for a few days until you cycle the engine like 25 times or so. The O2 sensor should get rid of all your codes, though.

 

[Jim311]

Oh.. and you can remove and replace the O2 sensor easily without jacking it up. I just crawled under my Jeep and did it. Took me 5 minutes tops and got rid of my codes. I saw a little increase in gas mileage as well.

 

[JordoVR]

Great! Thanks for the help guys and especially to you Jim... nice and detailed! I'll get on changing that O2 sensor asap now. Thanks again!

-Jordo

 

[Jim311]

No problem. I don't know too much.. but when I do I try and share with those who need it.

 

[JordoVR]

Oh yeah... Sorry again... But are there any special tools I need to replace the sensor? What sizes? Thanks

-Jordo

 

[Jim311]

Well, they do make a wrench for removing O2 sensors, but most of us ******** here just use an adjustable wrench. That's what I used. It might take a little elbow grease to get out since it's constantly being heated and cooled over it's lifetime. Other than that there's no special tools or anything.

 

[JordoVR]

Damn... for some reason I am having the hardest time getting the friggin wiring harness off! I don't know if my hands are just too cold or if I am not depressing a release or what. It's kind of tight up in there and night too so I'm using a flashlight. I'll have to keep trying and see if daylight helps more.

 

[Jim311]

Yeah, it's a real pain seperating the two pieces. I think there's a little clip on one side that you have to pull to get them to seperate. I think I used my pocketknife or maybe a pair of pliars. It's kind of a pain to get apart.