Check engine light, O2 sensors

[JIMBOJAMES]

Ok so I got the code for O2 sensor being bad. I changed the precat one and the light is still on. The shitty haynes book says you need a techinican to reset the computer. Is this true? I disconnected the battery but the light came back on in 5 minutes. Someone told me the downstream sensors doesnt do much. Is this true too? I dont really want to spend the money right now, since Advanced auto ripped me $75 for the pre cat sensor. I would appreciate the help. thanks

 

[Kejtar]

Ok so I got the code for O2 sensor being bad. I changed the precat one and the light is still on. The shitty haynes book says you need a techinican to reset the computer. Is this true? I disconnected the battery but the light came back on in 5 minutes. Someone told me the downstream sensors doesnt do much. Is this true too? I dont really want to spend the money right now, since Advanced auto ripped me $75 for the pre cat sensor. I would appreciate the help. thanks

Maybe your wiring is bad? It could also be that the 2nd sensor is tripping it too.

 

[Bryan C.]

The downstream o2 sensor(after cat) is in place to monitor the catalyst efficency. what year is your XJ? What code are you setting? Do you have a scanner or are you using the blinking check engine light method? $75 for a sensor iisn't that bad, well compared to a dealer unit. I think ketchup is right and it most likely is a bad downstream o2. Or possibly it just might be a blown fuse for the o2 heater circuit. Do yourself a favor and use a test light and check all you underhood fuses before spending any more money.

 

[JIMBOJAMES]

Alright I'll check the fuses because I had blown a fuse last week, maybe a different one blew. I'll check it out. Thanks

 

[BCKNBLK]

Start w/ the simple and cheap (fuses), I'll agree w/ that. Frankly though, 50 to 75 bucks for an oxygen sensor is average. I've always bought the Bosch brand, about 55 bucks, and never had a problem w/ them on any of my cars. The oxygen sensor after the cats is just as important as the pre-cat oxygen sensor. At this point, since you now have a new oxygen sensor, try switching their positions and see what reaction you get. I have had more situations where the light has reset itself upon me fixing the problem, than I have had situations where the light had to be reset by the scanner computer. If you are going to do any decent amount of work on modern auto's, get a scanner that handles as many different systems as you can. They really do pay for themselves after a while, in more ways than one!

 

[JIMBOJAMES]

ok I am gonna switch in the one for the rear, but are they the same? I the only different I noticed was a heat shield. I had the code 138 which in my book just says its a bad O2 sensor, but on Jeep horizon it says it is bank 1 sensor 2 is that the one in the cat?

 

[sw_mi_xj]

just happen to have my scan tool handy ,
p0138 : O2 sensor circuit high voltage ( bank 1 sensor 2 )
sensor 2 is the post cat sensor
what year is this ?

 

[BCKNBLK]

Not sure what year this is for, he didnt say. But he said in the beginning that he had the new oxygen sensor in the pre-cat position. SO, Jimbojames, take that new oxygen sensor and put it in the post-cat position and see what happens. More likely than not the computer will reset itself upon the problem being fixed, once it does its test right before you start the engine.
Let us know what happens...

 

[langer1]

The year's important because some years have 3 pre-cat sensors

 

[Smith2000]

My 2000 got this repair not too long ago -- also P0138. Like was said above, sensor 2 is the post-cat. The pre and post cat sensors are not the same part, at least on mine. I used Bosch sensors, their part numbers are different, and holding the two in your hand you can see they are different.

 

[jeep-noob]

got the same P0138 code on my 2000.
whats the diff between OEM and universal, other than half the cost?
http://www.napaonline.com/masterpag...gen+sensor&KeywordCat=Oxygen+Sensor&VehCode=Y
will the universal make passing smogg less certain? that would be one of the bigger concerns for me.
thank you

 

[langer1]

got the same P0138 code on my 2000.
whats the diff between OEM and universal, other than half the cost?
http://www.napaonline.com/masterpages/NOLMaster.aspx?PageId=430&Keyword=oxygen+sensor&KeywordCat=Oxygen+Sensor&VehCode=Y
will the universal make passing smogg less certain? that would be one of the bigger concerns for me.
thank you

With the universal one you will need to cut the plug off and wire it in direct, I would not start chopping wire on a 2000.

 

[jeep-noob]

With the universal one you will need to cut the plug off and wire it in direct, I would not start chopping wire on a 2000.

could i cut the plug off of the bad o2 sensor and connect to the new one? that way the wire to the computer stays intact.

 

[langer1]

could i cut the plug off of the bad o2 sensor and connect to the new one? that way the wire to the computer stays intact.

Yes.

 

[UNCC_99XJ]

ok so apparently this is the time of year for XJ's to throw this particular code. I got a CEL a little over a month ago with the came code. When I hooked it up to my dads scanner, which was within 5 minutes of the light coming on, everything read fine. All the sensors were reading normal. We turned the light off and it stayed off untill last weekend, when I was of course, 4 hours away from home. I guess i'll go ahead and replace the sensor and that should fix the problem?

 

[anony91xj]

Yes, a new sensor will fix the problem 90% of the time. The light won't go out when you just fix the problem though. It'll take 50-100 drive cycles (as long as a month of driving) for that light to go out, unless the memory is reset with a scan tool, in which case it'll take 50-100 drive cycles for the computer to completely relearn all its perameters.

 

[UNCC_99XJ]

cool deal. My dad has a scanner that also does a DRO so I can see what all my sensors are reading and whats doing what while the engine is running, so I can turn the light off whenever I want, which is what ive done the past couple of times.