i have a 2000 xj, with about 140,000 miles on it.

my check engine light goes on and off, when its on, I had it read and it came back "to much voltage o2 sensor bank 2" which i was told is the 2nd o2 sensor behind the cat

my jeep runs like a top, mileage is really good actually, i get just about 300 miles to a full tank of gas, normally about 275 with normal driving

like i said, runs good, gets good mileage

so why is the light on and what do i do to fix it?

send any replies to my email please

scotts2887@gmail.com

thanks scott

 

are there any ideas what this could be?

somebody has to know

 

can you the actual p code? a 2000 has 4 sensors and 2 cats just want to make sure your getting the right one

 

no i will get it tommorow if i can, and i have only seen 1 cat under my jeep, kinda looks like a oversized popcan, i dont think i have too, maybe i just didnt look enough

i will see what it comes up as

 

ok just found out the 4 cat one is cali emissions one. if it only has 2 o2 sensors the code discription should be like bank 1 sensor 2 an I6 only has one bank, unless it has more than one converter

 

yea i forget, i got i read like a month ago, i asked the guy what that meant and he just said that my 2nd o2 sensor is bad, but what i dont get, it says to much voltage, and if my o2 sensor is bad, why am i getting decent mileage out of my jeep, if it was going bad, i would assume that my mileage would suck

anyway
thanks for the info, i will get it checked out tommorow

 

the second sensor is only there to monitor the efficency of the cat. converter if you dont mind the cel i say let it ride.

 

It is most likely the after cat oxygen sensor itself. This one only measures efficiency of the catalytic converter.

Oxygen sensors have a finite lifespan of 100k-150k. If there is any question, replace this sensor. And while you are at it, if you're going to keep the vehicle, replace the pre-cat sensor as well as failure of it is probably not far behind.

Seek out a name brand sensor like NTK or Bosch. Stay away from the no-name cheap charlie crap on ebay. It is absolute junk.

 

ok guys, i got the code, and here is what the paper says

p0138
definition:circuit condition (heated oxygen sensor bank 1 sensor 2)

explanation:the powertrain control module uses the 02 sensor to calculate air/fuel ratio in the exhaust

Probable cause: 02 sensor is defective
fuel system is running rich or lean
engine misfire
fuel pressure to high or low

that is what the paper says

here is what i did today, first i cleaned the throttle body, it was dirty, not bad for 140,000 miles, but still dirty...i got is really clean, then i ran the jeep for about 30 min, then replaced the front o2 sensor and the rear 02 sensor (the front was a ntk and the rear was a bosch) dont think that matters, but anyway....they are both brand new with a clean throttle body and a new air filter...still got the code

now what?
the guy at autozone who ran the code says that the computer might take a while to realize the new sensors, but he said i should pull the battery cables off, to reset the system. I dont have a problem with that if it will help, but if that wont help at all, then i just erased all my radio settings for nothing

anyway let me know
thanks
scott

 

Do you mean you still have a check engine light ON? If it is, it is likely that there is still a problem.

However, if the check engine light is off and the code is still there, that would be normal unless you CLEARED the codes.

I'd perform a comprehensive inspection of all wiring related to that sensor. If there is a short anywhere along that circuit, you could get that code.

 

no i still have it, same as before, it does go on and off randomly, the guy said it might take some driving for the jeep to realize the new o2 sensors
he also said to unhook the battery for 10 min, but im not sure that does anything?
what do you think?

 

You could try the below procedure. If it still does it after this, the problem still exists and you need to continue to look for the root cause.

---------------------------------------

This procedure is for OBDII Jeeps.

This six step procedure will erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed. After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

Perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

1. Disconnect the POSITIVE battery Terminal and touch it to ground for 30 seconds. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.
2. Reconnect the Battery Cable
3. Turn Ignition Switch to the “On” position but DO NOT start the engine
4. Turn Headlight “On”
5. Turn Headlights “Off”
6. Turn Ignition Key “Off”


The PCM Adaptive memory has now been flashed, or erased from the PCM.
When you start the engine it will be running off a set of pre-programmed values that come with the PCM from the factory. When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”. The PCM will collect data for Adaptive Memory for the first 50 warm-up Cycles.

 

ok i will try that, kinda of wierd way to do it, but i guess its worth a try

thanks for the info, do you think this will improve performance and mileage (the reset computer thing)

 

it worked thank you

 

so a new o2 sensor cured this code? i have the same code but it looks like someone jb welded it to the cat!