johnlocke

So I got a check engine light on my '01 XJ. The Catalytic converter has just been replaced, and the codes are saying stuff that point to the cat or the o2 sensors closest to it.

So I just replaced the two O2 sensors that are accessible from under the jeep. Easy enough. While I was under there, though, I thought I saw two /more/ up above the cans that the header goes into (sorry, don't know what they are ... collectors?). Where the three pipes join into two, there's a sensor of some kind with the electronics run up towards the fuel rail electronics. Then there's this can, and then the o2 sensor on each pipe I replaced. I don't know what those sensors are! 4 O2 sensors?

Second question (related) is, do I need to unhook the battery to reset the light, or will the light go out after X number of minutes if I've fixed the problem?

builtnotbought89'

U can just go to auto zoo or ur local parts store & have them clear the codes then if it comes back on take it back to they & have them scan it again & see what trouble codes come up!!!
Good luck!

captainwoot

Maybe this will help, and yes you will need a scan tool to clear codes.

Various DTC's :Explanation of SAE terminology for Oxygen Sensor or Catalyst location.;This is information only.System or ComponentDTC / Error Message;Group 18 - Vehicle Performance / DriveabilityRecommendationExplanation of SAE terminology for Oxygen Sensor or Catalyst location. SAE terminology for Oxygen Sensor or Catalyst Location is relatively simple, but has sometimes been misprinted. One of the Federal requirements of OBDII is common terminology between manufacturers. Once you understand the terminology, it doesn't matter whose vehicle you are working on. The basic designation is expressed as follows: X/Y X or the first number indicates which cylinders are involved. If this number is a 1 (one) this indicates that this code deals with cylinder number one. If an oxygen sensor for example is in the exhaust stream for the number one cylinder; then the designation would have a one in the first position. If the 1st position of the designation is a 2 the following applies. On a V type engine the 2 will correspond with the bank opposite number one cylinder. Which will also be number two cylinder on a Chrysler product. NOTICE THERE IS NO MENTION OF RIGHT OR LEFT. Chrysler uses a numbering system where #1 cylinder is the one nearest the front of the engine, The next cylinder back is cylinder #2. Manufactures other than DaimlerChrysler use other numbering schemes for cylinders. Even if the engine is numbered 1-4 on one bank and 5-8 on the other bank; a 2 in the first position of the SAE designation would indicate the bank of cylinders opposite of number 1 cylinder. Inline engines with a split exhaust system still follow this designation. A Jeep 4.0L engine in some model years is equipped with a front and a rear exhaust. The front system (cylinders 1,2,3, these will be indicated by a one in the first position) and the rear (cylinders 4,5,6, these will be indicated by a 2 in the first position). The Y or second position following the forward slash "/" in the designation indicates the relative location of the oxygen sensor from the cylinder head. A number 1 indicates an oxygen sensor that is the closest to the cylinder head, and the number gets larger the further away from the cylinder head that it is located

johnlocke

Well, as mentioned, I replaced /two/ of the sensors. After driving for a bit today, the light went off all by itself, so no need to clear it.

And just as an FYI for you guys (built), autozone and none of the other guys will clear the sensor. Maybe someone you guys know will, but I've asked this before and it's always a no go. They're not allowed to clear it themselves (though you can rent the tool from them for five minutes and do it yourself if you want to).

I also was told by some guys today that it might be possible to have 4 O2 sensors if the jeep was built for california emissions. I have no idea if this is the case with mine, but I'm going to look into it!

EndlessMtnFab

The 2001 does indeed have 4 sensors.


1 sensor for each "bank" of cylinders (3 cylinders per bank).


Then a sensor where the collector is (where all 6 end up joining).


And then a sendor in/after the catalytic converter.



Joe

johnlocke

That's a bit odd because I found them in different locations.

So I saw one on each bank up near the block. Then, there was another one on each bank beneath the collectors (if that's what the cans on each bank are). That's it. Nothing anywhere /near/ the cat or muffler or any further back than the front of the transmission.

captainwoot

I think for thatyear there are 4 sensors 1 upsteam for cyl 1-3, 1 upstream for cyl 4-6, 1 downstrean cyl 1-3, 1 dowmstream cyl 4-6, those cans are actually convertors

johnlocke

That jives with what I saw. Don't know much about converters, but I'd be glad to use the right terms

EndlessMtnFab

Then I must be imagining things.



Unless I'm thinking of a 99-00 ? I know I've seen the 4 sensor setup with one in the converter.



I"ll look at the FSM's tomorrow night and see what diagrams I can find.



Joe

fantic238

See, that's why Renix is better, only 1 sensor and no confusion, and in some cases (mine) no sensor at all and no cat (stock).

johnlocke

http://www.4x4xplor.com/O2-sensor.html

Found this to show that 4 sensors on (at least my) jeep is almost certainly CA emissions. There's two upstream of the mini-cats and two downstream.

GoreXJ95

This should help...

fantic238

that's for a v8...

johnlocke

Ha! Agreed. Took me a second to notice .

But it does visually illustrate a question I have for anyone else still reading this thread:
https://www.cherokeeforum.com/f2/can...81/#post285655

I'd like to know on my (what appears to be) cali emissions vehicle if I can get new headers. Obviously, I'll be moving O2 sensors around, and with ODB2 sensors, I need a sensor pre and post cat. Do other '01 cherokees have their ODB2 sensors pre and post cat (as shown above), or do they also still have them in the headers somewhere? I'd love not to go get custom pipe made if I look at doing this (this: removing the cali emissions and going down to 2 O2 sensors and losing the converters that are in my headers, which is all perfectly legal in my state).

BlueXJ

Don't think your electronics will support an O2 reduction like you want. Not sure but from what I have read it won't.