P0500 nuff said

[Jbergun]

If your not throwing P0700/P0715/P0720 it's not the trans input/output speed sensors.

You may need to have a actual scanner pull the codes,most code pullers will not pull trans codes beside P0700.

The rear wheel speed sensor produces a AC signal,you need a scope to properly test it and they are not cheap.

2 cheap and easy known fixes on a KJ for P0500.

1-Remove diff cover,clean inside of the housing very good.This may take 4-6 cans of brake cleaner.Make sure any trace of metal and/or clutch material(if you have the trashloc) are gone.

2-Replace sensor with OEM only sensor then re-seal and refill diff with proper gear oil and/or friction modifier(if you have the trashloc).


If that fails to fix the issue get a new pigtail connector from the dealer and pull the rear seats out to access the rear connector located under the left rear seat.Run new wires from that connector to the wheel speed sensor.Make sure to twist the wires like in the pic below(granted you will only have 2 wires).

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Can i like this ten times? Thank you.

 

[Jbergun]

Serviced my diff and did as instructed. I used about 4 cans of brake clean everything looked brand new after that. The code has not come back but the jeep is still running and idling like crap. When i do get it to idle and i try to drive it dies as soon as i am done accelerating. The only code i am currently getting is for the oxygen sensors. I removed them and they were dirty. I cleaned them up with gasoline and a brush. Still running likw crap still getting the o2 codes.

 

[uss2defiant]

it might be worth the time and money to get it diagnosed then you do the fix.

 

[Jbergun]

it might be worth the time and money to get it diagnosed then you do the fix.

I agree man i have to find a trustworthy shop. I havnt personally had to use a shop for much of anything.

 

[tjkj2002]

You can't clean O2 sensors,you just replace and I'll just remind you to only use NTK O2 sensors.

If I remember right 50psi fuel pressure is not enough,needs to be 58psi if I believe.

Now a tricky test that I would not recommend on a '02 KJ but as long as you don't run it for to long and to high of speed it should be okay.

Take both upstream O2 sensors out,unplug them also.Start it up and take for a short drive.If your rough running and idle issues go away you have plugged cats.Just be careful because that drivers side O2 bung will exit exhaust right on the heat shield covering the EVAP and fuel lines.

 

[Royy]

What specific codes are you getting for the O2-sensors?

Are your fuel trim levels fine? Even most basic code readers have a 'live data' option that allows you to check these.

 

[Jbergun]

You can't clean O2 sensors,you just replace and I'll just remind you to only use NTK O2 sensors.

If I remember right 50psi fuel pressure is not enough,needs to be 58psi if I believe.

Now a tricky test that I would not recommend on a '02 KJ but as long as you don't run it for to long and to high of speed it should be okay.

Take both upstream O2 sensors out,unplug them also.Start it up and take for a short drive.If your rough running and idle issues go away you have plugged cats.Just be careful because that drivers side O2 bung will exit exhaust right on the heat shield covering the EVAP and fuel lines.

That was my plan for tomorrow to get new o2 sensors in. I will try the drive around the block with them out. I just want to know what it is good bad or other wise. I am not sure exactly what the fuel pressure was my father in law needs glasses that he doesnt wear in the garage. I know he said it was over 50psi. I was starting it as he read the gauge. I still have it rented from autozone so i can double check that.

Thanks for the help.

 

[Jbergun]

What specific codes are you getting for the O2-sensors?

Are your fuel trim levels fine? Even most basic code readers have a 'live data' option that allows you to check these.

P0141 and p0161 i use an obd2 elm327 so i can see the o2 voltage reading and before i tried cleaning the sensors it stayed pinned pretty high. Now they go up and down then just down then zero.

 

[uss2defiant]

didn't you recently change your o2 sensor?

 

[Royy]

P0141 and p0161 i use an obd2 elm327 so i can see the o2 voltage reading and before i tried cleaning the sensors it stayed pinned pretty high. Now they go up and down then just down then zero.

Which ones? The upstream sensors? Downstream? All four of them?

The upstream ones are supposed to continuously switch between high and low values pretty fast. The downstream ones should stay pretty steady at a relatively high value.

Your codes are for both of the downstream sensors.
With those codes, I'd make sure the wires on your downstream sensors aren't twisted, and are not getting too hot due to being too close to the exhaust pipes.
Based on my (limited) experience, I don't think those codes are caused by bad cats. I've dealt with actual bad cats on my KJ twice, and they always caused other O2-related codes, but never those.

 

[Jbergun]

didn't you recently change your o2 sensor?

No i have never replaced the o2 sensors on my kj.

 

[Jbergun]

Which ones? The upstream sensors? Downstream? All four of them?

The upstream ones are supposed to continuously switch between high and low values pretty fast. The downstream ones should stay pretty steady at a relatively high value.

Your codes are for both of the downstream sensors.
With those codes, I'd make sure the wires on your downstream sensors aren't twisted, and are not getting too hot due to being too close to the exhaust pipes.
Based on my (limited) experience, I don't think those codes are caused by bad cats. I've dealt with actual bad cats on my KJ twice, and they always caused other O2-related codes, but never those.

In 2002 we only got 2 downstream sensors if i am not mistaken. They are right after the cats. I had watched the trims before and they would jump around. I figured it was normal because she was running normal.

 

[tjkj2002]

In 2002 we only got 2 downstream sensors if i am not mistaken. They are right after the cats. I had watched the trims before and they would jump around. I figured it was normal because she was running normal.

You have 4 O2's,2 before the cats and 2 after.

The 2 upstream O2's on a '02 KJ are a pain to get to.

 

[Jbergun]

Yea i just figured that one out. I cant get the drivers side without an o2 removal tool. I did removed the downstreams and it actually seemed to start and run better. Could this be a sign thats the problem. At first i started without the two down and the passenger side upstream. Started good loud as hell but started and didnt seem to be vibing as much. Put the upstream in and gave it a shot with just the two downstreams out. Drove it a little and it seemed better. The brake pedal is still hard as rocks.

 

[tjkj2002]

Yea i just figured that one out. I cant get the drivers side without an o2 removal tool. I did removed the downstreams and it actually seemed to start and run better. Could this be a sign thats the problem. At first i started without the two down and the passenger side upstream. Started good loud as hell but started and didnt seem to be vibing as much. Put the upstream in and gave it a shot with just the two downstreams out. Drove it a little and it seemed better. The brake pedal is still hard as rocks.

With the downstreams removed that 3rd non-monitored cat maybe the issue,really need to try with just the upstreams out.

As far as the hard brake pedal make sure the vacuum line to the booster is on and the booster is getting good vacuum,also check that booster check valve.If the check valve and vacuum line(and vacuum) is good you may have a bad booster.

Easy test for the booster is to get in the Jeep,engine off,and pump the brake s a few times,then hold the brake pedal down firmly and start the engine.The pedal should fall 1"-2" and then hold steady.If it does not drop you have a bad booster and/or vacuum issue.

 

[Jbergun]

With everything hooked up i am getting good pressure out the tail pipe. With the rpms up a little the brake feels normal. I will have to see if my neighbor or father in law has a wrench for the o2 sensors. You still think its worth the money to replace the downstream sensors i am getting the codes for? I cleaned them and they already had some black soot on them after only a few starts. I would hate to replace them and they fail because of something else.

 

[uss2defiant]

I think autozone has the o2 wrench on the loaner program.

 

[tjkj2002]

With everything hooked up i am getting good pressure out the tail pipe. With the rpms up a little the brake feels normal. I will have to see if my neighbor or father in law has a wrench for the o2 sensors. You still think its worth the money to replace the downstream sensors i am getting the codes for? I cleaned them and they already had some black soot on them after only a few starts. I would hate to replace them and they fail because of something else.

Don't replace the O2's until issue is fixed first,bad O2 sensors will not cause the engine to stall,run rough,or any of that.

Even with all 4 O2 sensors removed,and unplugged,the PCM will just go into cold start mode,a known setting for safe cold running and just a tad on the rich side to be safe.

 

[Jbergun]

Started it up today and inspected under the hood while i had it running to look for anything out of the ordinary. I dont know for sure but this doesnt seem normal.

https://youtu.be/PbFj4SYLtY4

I am at the same spot as i was before two upstreams in two downstreams out (o2 sensors)

 

[uss2defiant]

probably helps to post the correct YT link