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Old 03-10-2015, 04:47 PM
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o2 Sensor

Hey,
Im a little bit of a noob when it comes to these things, but I'm trying to learn.
My check engine light came on and gave me a code for my bank one o2 sensor.

Which one is my bank one sensor? Does anyone have some pictures of where its at in under the hood? And could somebody possibly post a link to the right part please? Unless anyone says differently I think i would like to go oem.

Thanks for the help in advance

2000 Wrangler 4.0 Automatic

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Old 03-10-2015, 05:51 PM   #2
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I too will be following this link. I have 2 bad sensers

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Old 03-10-2015, 06:48 PM   #3
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Each bank has two sensors. You need to figure out if it is sensor one (before cat) or sensor two (after cat). I've attached a diagram for the federal emissions layout, which has 2 O2 sensors total, as well as a California emissions diagram, which has 4 O2 sensors total (bank one and bank two).
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Old 03-10-2015, 08:26 PM
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Thanks for the response.

The spot before the cat (upstream) has no sensors. It just has two bolts in the place of the sensors. Is this because it's not a california jeep?
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Old 03-10-2015, 10:00 PM   #5
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Thanks for the response.

The spot before the cat (upstream) has no sensors. It just has two bolts in the place of the sensors. Is this because it's not a california jeep?
It's got to have upstream sensor(s) somewhere Updtream sensor are used for the PCM to calculate fuel mixture.
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Old 03-11-2015, 12:24 AM   #6
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Unless someone removed them.

Do you see any electrical plugs that are not plugged into anything?
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Old 03-11-2015, 12:56 AM   #7
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I just replaced both of mine about an hour ago. Since yours is a non-Cali like mine make sure you get the right sensors, Autozone sold me the wrong downstream sensor twice, they have something different in their system. Bosch 13122 for upstream and 15465 for downstream. The sensors are literally just on either side of the cat, you just gotta look for them. Downstream was kinda hidden because of the skid plate. Upstream just sits on top of the pipe right next to the frame.
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Old 03-11-2015, 08:53 AM
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I'm not sure if there are any plugs not plugged in. I'll have to check later. (Jeep was pretty much undrivable)

If the were unplugged wouldn't that mean it wouldn't have run good at all since they were out?

Where would the sensors be if they weren't in the two wholes above the mini cats?

It runs really bad. Doesn't get either fuel or air. Not exactly sure which.

So if the sensors help calculate fuel mixture wouldn't they be on the intake? Or before the engine?
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Old 03-11-2015, 09:53 AM   #9
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Quote:
Originally Posted by gmiller0737 View Post
It's got to have upstream sensor(s) somewhere Updtream sensor are used for the PCM to calculate fuel mixture.
Newer TJs like the OP's have four 02 sensors, one each upstream & downstream for each of the two mini-cats as shown in the first illustration. And to the best of my knowledge, most TJs shipped 50 state compliant.

That second illustration is not one I've even seen, what model and model Jeep is that from?
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Old 03-11-2015, 11:54 AM
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Newer TJs like the OP's have four 02 sensors, one each upstream & downstream for each of the two mini-cats as shown in the first illustration. And to the best of my knowledge, most TJs shipped 50 state compliant. That second illustration is not one I've even seen, what model and model Jeep is that from?
That's what I thought. However when I looked for the upstreams (right above the mini cats like I the picture below) there are just bolts filling the hole. No sensors at all. Does this mean the po moved them? I'm stumped at this point.

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Old 03-11-2015, 01:57 PM   #11
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That second illustration is not one I've even seen, what model and model Jeep is that from?

Both illustrations are from Alldata, the second was described as a federal emissions setup for a 2000 Wrangler 4.0L.
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Old 03-11-2015, 02:00 PM
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From what I see, unless the two sensors pictured above were relocated, it looks a lot like this diagram. The diagram was labeled as a 94-04 Cherokee 4.0.

If that picture works than you can see that there are only two on the exhaust pipe if thats what you call it, and they are both bank one. So I really don't know what I'm talking about, but if this is the case and there are only two, how do i tell which one is bad? Or do i just replace both?

Like I said I'm a little clueless but I need an answer pretty quick because i don't have a vehicle right now
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Old 03-11-2015, 02:24 PM   #13
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You need to post the code that you got for us to be able to identify which sensor you are having an issue with. The code will reference bank one sensor one (1/1) or bank one sensor two (1/2).

I can't see your diagram, was this the one you were referencing?

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Old 03-11-2015, 03:28 PM
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Yes. That was the one I was referencing. I had the code checked and all the guy told me was bank one. I'll have to either rent a reader and read it again or I might just replace both. I think that's what I might do just to prevent future problems.

If I were to replace both, what brand would you recommend? Could someone post a link or part number for both please? Is the diagram correct in that there are only two and the are both to the rear of the vehicle and not near the engine? I have found both the sensors just looking around.
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Old 03-11-2015, 03:53 PM   #15
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Are the 2000 model TJ's able to pull codes on the dash?

If not and you have an android phone you can buy the torque pro OBD II app for $5 and get a bluetooth adapter for $20-$30 so you can read codes and live scan data. If you have a laptop you can download free scan tools, such as romraider, for free all you need to do is get an OBDII cable.

Usually front O2 sensors fail more often than rear sensors simply because they are subject to more frequent and rapidly changing temperatures where as the rear O2 sensor is behind the CAT where there is a more stable temperature. So if I had to guess I would say the replace the front sensor. But rear sensors fail too.

As for brand, go with NTK which is made by NGK. Go to the NGK website and type in your make, model, year, etc and find the right part number.
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Old 03-11-2015, 04:28 PM
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So would the right part be the precat (third one down) and the post cat (sixth one down)?

Pre car being toward the front of the jeep and post being towards the rear?

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Just want to be sure before I pull the trigger.
Thanks so much for all your help
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Old 03-11-2015, 04:35 PM   #17
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Yes, that looks correct to me.
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Old 03-11-2015, 04:40 PM
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Alright! Ill order a set right away! Cant thank you enough
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Old 03-11-2015, 08:37 PM   #19
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2000 besides having a crack prone head must have been a transition year with federal 2 sensors and calif 4 sensors

The 4.0 calif in 98 has only 2 one upstream and one downstream
The federal one in 2004 has 4 with two upstream and two downstream

I always avoided 2000 as I did not want a 4.0 with a crack prone head
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Old 03-25-2015, 02:59 PM
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Ok. So bringing back the thread, here's my issue

I ordered the front ngk sensor. I ended up not being able to get the old one out so I just took the jeep in. I figured the $25 bucks was worth not having to deal with it as I don't have a real good shop down here.

So I picked up the jeep with the new front sensor newly installed and as I was driving out of the lot the check engine came back on. So I turned around to get the code checked and apparently the second sensor( the one after the cat) is fried now.

Is this just a total coincidence or is something else wrong. Is it possible that the computer is putting too much current through the sensors? Anything else I'm missing? I still haven't totally solved why there are no upstream sensors?

This jeep is giving me a headache
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Old 03-25-2015, 05:03 PM   #21
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It's not likely to be an over-current problem with the sensor. The heater elements are bench tested at 14 volts continuous and will stand a few more before burning out. The sensor side produces voltage which is read by the ECU.

Driving out of the mechanic's lot and having the other sensor fail is an odd coincidence.

The after cat sensor simply monitors the condition of the catalytic converter and won't have an effect on vehicle operation.

O2 sensors are typically tested through a 100,000 mile life (it's a fed requirement) and don't just fail without something else going on. Those things can be:
Somebody ran leaded gas in it
Somebody ran crappy gas contaminated with known sensor fouling agents (like silicone)
Somebody re-flashed the ECU and there is no warm up strategy (this lets the heaters get hot before all the moisture is purged and cracks the ceramic sensor
The sensor wires are not sealed at the connectors. O2 sensors need a very small amount of reference air on the cold side of the exhaust which is typically replenished from the air in the wire harness. Water seeping in at the connector will wick through the wires and cause bad voltage readings from the sensor
Somebody hit the sensor hard enough to crack the ceramic element (equivalent to dropping it on a concrete floor from a height of 1 meter or more, I forget the G loading for that)

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Originally Posted by tisney View Post
Ok. So bringing back the thread, here's my issue

I ordered the front ngk sensor. I ended up not being able to get the old one out so I just took the jeep in. I figured the $25 bucks was worth not having to deal with it as I don't have a real good shop down here.

So I picked up the jeep with the new front sensor newly installed and as I was driving out of the lot the check engine came back on. So I turned around to get the code checked and apparently the second sensor( the one after the cat) is fried now.

Is this just a total coincidence or is something else wrong. Is it possible that the computer is putting too much current through the sensors? Anything else I'm missing? I still haven't totally solved why there are no upstream sensors?

This jeep is giving me a headache
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Old 03-25-2015, 05:48 PM   #22
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Perhaps with the new upstream better controlling the mixture the poor function of the downstream sensor was more pronounced and noted by the PCM so a properly functioning upstream sensor may have made poorly functioning cat or downstream sensor easier for OCM to notice and you should not blame the repair facility for that
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Old 03-25-2015, 06:51 PM
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Thank you John and digger. That all makes good sense. He reset the code and the light is off for now. I will see if it comes back on and if it does I'll go ahead and replace it

One of you said it has no effect on performance. As I was driving back there was one point where the jeep started to lag. Like it wasn't getting enough gas (or enough air) would this be cause by the second sensor? It doesn't sound like it but if it's not I have a whole other issue I guess
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Old 03-25-2015, 08:47 PM   #24
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Just replaced both upstream O2 sensors, used NTK OEM. The ones I removed were hardly more than finger tight. Had a CEL about a year ago after changing my radiator fluid which involved multiple starts. I had it cleared and it came back a few days ago. Read the same P0153 code. I changed the upstream sensors and did a reset on the ECU.

The thing is, I have done but about 15 warm up cycles, the CEL still flashes after 15 seconds key on, no start. Hmmmm. That means it is not emissions test ready. Hmmmm.
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Old 03-26-2015, 06:25 PM   #25
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Read about not ready for emissions recall on 05 06 wranglers
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Old 03-27-2015, 12:01 AM   #26
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Read about not ready for emissions recall on 05 06 wranglers
Yes, I am aware of that letter dated in Sept. 30, 2013. Does anyone have the complete copy and instructions (the actual letter)?

I also have the SL 25-001-07 that was issued in 2007.

How do you determine the sales code? The SL 25-001-07 states it pertains only to Jeeps with sales code ED1 or ERH.
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Old 03-28-2015, 06:20 PM   #27
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I performed the SL 25-001-07 today, meh. We shall see, it did apply to my vehicle.
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Old 04-03-2015, 02:27 PM
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So I replaced the second sensor also, and reset the code. The light came back on, I had it read. It's a high voltage heater code for the 1/1 sensor. Having just replaced both that I have, what else could cause this code? Is the computer sending too much voltage or what?
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Old 04-03-2015, 02:39 PM   #29
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Post the code not sure if you mean high voltage sensor ( over rich mixture) or short in sensor heater circuit
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Old 04-03-2015, 03:32 PM
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This is the slip they gave me
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