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02 sensors

2K views 24 replies 14 participants last post by  xjpete 
#1 ·
2001 WJ 4.0 before anyone says which codes I'm not getting any,but the 02 sensors- any what range should they be replaced? I don't want someone to say- replace when your check engine light come on. I have 131,000 miles and based on the previous owners lack of maintenance they did on the Jeep,I'm thinking they were never replaced. They might be factory installed. So what range?-I know these things don't last forever.
 
#2 ·
I'm not sure about the life expectancy of an O2 sensor, but I know they can cause issues without setting a code. I've heard 100K, maybe someone will chime in soon with more info.

I replaced mine right after I got it. Had 225K miles, no proof they had been changed. Mileage improved and she ran much better.

Only buy Mopar sensors. @Kolak can hook you up if you need to replace them.
 
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#3 ·
`o2 sensors are messengers, you do not replace them just because you see a code - You overheat you dont change the temp sensor.

How is your jeep running?
You would be in the ball park as 100k is a good live expectancy. Others will say 150k just a professional judgement call, but 20yrs seams enough.

You will want to use NTK sensors.
 
#4 ·
I’ve always been told to replace them every 60k miles. I’ve had them go bad and not trip a code ( typically the downstream sensor) and usually you’ll get very very very bad gas mileage. Keep the o2 sensors fresh because they can destroy a catalytic converter
 
#5 ·
I see lots of high mile Jeeps with 150K plus on the original sensors still running with no codes or stored pre-code history but they generally run and perform poorly.

Changing them generally yields some positive results with noticeably better performance.

Use Denso or NTK when replacing them, try and avoid Bosch on the older models that run a pci bus communication line such as the WJ they don't play well with the pcm.
 
#6 ·
Yes my mileage is not what it was (16.5+) last summer. Currently getting 15.5 at best. I don't run A/C and this vehicle is maintained regularly. Will get some sensors this week.
 
#12 ·
I have CA emissions on my '04, so I have 4 (2 upstream, 2 downstream).

Pretty easy job. The upstream sensors require a some reaching, but nothing too difficult. I bought the sensor socket from Harbor Freight.

Look up the NTK sensors on Amazon and compare prices.
 
#8 ·
I've never had much luck using a socket on removing them. I spray/soak them with pbBlaster for a couple days and then put a pipe wrench on them beating the handle of the wrench with a hammer going between loosening and tightening until it breaks free. If you have a torch to heat the bung up, even better (just dont burn stuff lol). I haven't done one on a jeep, so I cant say for sure how well getting a pipe wrench up in there works.
 
#10 ·
Advance Auto has a great 02 Sensor Removal loaner kit which makes this job a breeze.
The sockets (a variety of 3) are extremely heavy duty and will not open up (e.g. spread) not matter how tight the 02 sensor.
I just went ahead and purchased it and use it for other applications as well.
Highly recommended.
 
#13 ·
While my 04 4.7 has Federal & 50 state emissions it still has 2 upstream and 2 downstream oxygen sensors.

The sticker under my hood says Federal as well as the info/sales codes on my build sheet as seen below.

NAS 50 State Emissions
NBGP Federal Tier 2, Bin 9A Emissions

On all our other present/past Jeeps (all 4.0) I used NTK o2 sensors with same part numbers as the OE sensors.

But when I bought my 04 4.7 WJ 8 years ago it had Denso o2 sensors in it so that's what I replaced them with. About half the price as NTK and I always heard some of the OE brands were Denso or NTK.

I always have had problems with the smell of non-burnt fuel on start up but don't think this has to do with the Denso o2 sensors. Could be leaking injectors or something like that and I have new Mopar TPS and IAC sensors. My mpg average is 18 so the o2 sensors must be working have descent.

On the deep-well 6-pt oxygen sensor socket I have the first thing I had to do was file down the sharp edges on the wire slot edges so it doesn't cut wires. But I still don't like to use it to install new o2 sensors.
 
#15 ·
Interesting Waterluvr and thanks for the info.

The below info for oxygen sensors and exhausts from wjjeeps is incorrect for my Fed emissions 04 4.7. As already mentioned I have 2 upstream and 2 downstream oxygen sensors when it isn't CA emissions. Those 4 o2 sensors are before/after each small cat (2) under the engine and they're showing those small cats only for CA emissions.

http://wjjeeps.com/oxygen.htm

Plus my OE exhaust never had a cat in front of the muffler as shown in the below diagram for Fed emissions and there was just a large muffler.

I believe wjjeeps gets a lot of their info/diagrams from the FSM and official parts manuals. Jeep/Chrysler never was big on keeping their FSM's updated from year-to-year and most often just used the same info as the previous years.

The below diagram from wjjeeps is the exact same one in my 04 FSM (p.14-40) which wasn't ever updated showing 2 small cats on the Federal emissions 4.7. Oh well, what you physically see is what you get!

BTW, the torque spec for oxygen sensors is 22 ft.lbs in case anybody can squeeze a torque wrench up in there. I just tighten them until they feel right and use the copper non-seize on the threads if it comes with them.

Below is the diagram mentioned before from wjjeeps and from the 04 FSM (p.14-40) which isn't correct for my Fed emissions 04 4.7. Since xjpete who started this thread has the 01 4.0 I might as well throw in the image for oxygen sensor locations on the 4.0 too.
 

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#21 ·
I have a 2000 4.7 with Federal Emissions (2 sensors), can you tell me the difference between the front and back sensors? Do both of them send data to the cpu affecting the engine or is it just the front sensor?

I'm looking to swap these out as preventative maintenance (168k), do you recommend spending more on Mopar sensors or is there other brands that you would recommend?
 
#16 ·
Bought a TJ with 150k. Put in a new motor and it was just not running quite right even with no codes.

Using my hptuner I noticed a lot of reads looked wrong. Two things can cause that-motor problems or the sensors giving the computer bad information. I started changing sensors and noticed the readings changed and the motor started running better. I am now in the camp of changing sensors regularly. Best guess is to do it about every 100k or when an issue related to sensor information makes the engine run funny. The computer will adjust engine parameters based on the sensor readings it gets so a sensor that is off even a little bit can make your engine run less than optimal.
 
#17 ·
A slight Thread Jack...I purchased 4× 4.7 oxygen sensors ($100 each) thinking I needed all of them, but it turned out I only needed two near the converter.
So, I have two brand new 4.7 Mopar sensors left over (I guess these are called pre-cats sensors).

If anybody wants them $50 each, or &90 for the two.
 
#18 ·
To ease removal, I've soaked the sensor a few days in (your favorite brand) penetrating oil. After a warm-up drive, I carefully crawl underneath with the exhaust still hot and carefully so as not to burn myself extract the sensor using my 02 sensor socket. The heat helps a great deal. But be very careful it is all hot. Thick leather gloves help in this situation.

I let the system cool before installing the new sensor.

However, on my Dakota I couldn't reach the sensor with any tools. So I left the old one in, cut a section of pipe out and welded in a new bung. The new sensor is in a place where I can easily reach it with my tools.
 
#19 ·
I replaced the 2 downstream sensors on my 2004 4.7L at ~75K and ~90K miles because they threw a code. One way is to change them when they fail. The other way is to change them ~80K (this varies depending what you read i've seen 60-100K). I prefer to change things on my own time. Given that you are at 130K, I'd replace all of them and be good for another 80+K miles.

You may get the old one out with a socket wrench if you cut the wire - but you are not going to get the new one in without damaging the wire and cutting& splicing is not recommended. Get the right tool for the right job - Since you are going to replace all the sensors at one time, you can buy/borrow the O2 tool than take it back....
J
 
#20 ·
Just wanted to know-why not the Bosch 02 sensors? I know years ago on my Yamaha motorcycle, the Bosch spark plugs didn't work well at all. NGK was OEM spark plugs and really every other plug didn't work right. On the other hand I believe my 97 XJ uses the Bosch 02 sensors. they work fine in there.
 
#24 ·
On the WJ series Jeep, in addition to other Chrysler products built at the time the one wire pci bus has some problematic data collision issues. You'll read plenty of accounts of DIY repairs that went poorly using the Bosch O2 sensors that were remedied straight away by replacing them with NTK or Denso.

In a shop environment we get them in all the time with running and driveability issues that stem from Bosch O2 sensors on this era of technology and the live data tells the rest of the story the pcm makes undesirable commands to the critical driver circuits based on the data it get's back from them.

You'll see a similar issue with these vehicles with regard to using aftermarket crank position sensors versus the OEM Mopar sensor. Ask anyone on this board and the only recommendation you'll get is the Mopar sensor at any price for a DIY repair.

I use piles of aftermarket crank sensors for tow in's late in the day on a Saturday every year during football season after the dealer parts are long closed for the day. They work fine so long as you own a scan and programming tool that allows the pcm to relearn the operating parameters of the aftermarket sensor.

Without the right tech, they are known to be very problematic for DIY use versus the plug and play Mopar part.
 
#22 ·
The downstream sensors work to monitor the health of the converters as well as to _protect_ the health of the converters. They can, and do affect fuel trim. I've seen people replace just the upstream sensors to resolve fuel economy issues and it turned out the downstream sensors were the culprits because they were countermanding the output of the upstream sensors.

So when you replace them definitely replace all of them. That said, the WJ sensors have exhibited very long lifespans, so if your check engine light is not on and you're not having fuel economy or closed loop performance issues then my suggestion is "if it ain't broke don't fix it" :)
 
#23 ·
Kolak-last summer driving my Jeep fuel mileage read between 16.4 to 16.8 and on highways was better on a long trip overall. I had to sit in traffic for maybe 15 minutes of stop and go driving and mileage only dropped slightly. Rebuilt transmission, new coil rail and I'm still getting 15. 8 maybe on my 10 mile ride to work that is mostly non stop driving. The previous owner didn't even change the bald tires, the torn axle boot, and I seriously doubt the 02 sensors were even replaced. The 1st time it went in the shop to change the torn axle boot,the mechanic told me the spark plugs were all different brands so he changed them. I feel if you are an owner of a vehicle if you cant maintain it properly,you shouldn't own it. The Jeep is being worked on as I have an infected foot and can hardly walk.
 
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