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O2 sensor


 
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TJ Apex
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Joined: 29 Jul 2005
Location: Mountains of SoCal. 6257 elev.

PostPosted: Fri Sep 11, 2009 8:02 pm    Post subject: O2 sensor Reply with quote

I have noticed my gas mileage going down the last couple months, it really tanked last week, and a couple days later my check engine light came on.
I had a friend hook his scanner up and it displayed PO155 O2 Heater circuit, bank 2, sensor 1.
My Haynes manual is no help telling me witch of the 4 sensors it is, and Auto Zone told me that there are 4 sensors, 2 before the cat and 2 after.
Being wide band sensors, these things are not cheap, so I need to make sure I get the right one.

Any suggestions would be much appreciated.
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2002 Wrangler Apex
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TJ Apex
Member


Joined: 29 Jul 2005
Location: Mountains of SoCal. 6257 elev.

PostPosted: Sun Sep 13, 2009 1:39 pm    Post subject: Reply with quote

I googled the PO155 code, and found a post from another site, and the person suggested to check the fuses that are under the hood for the O2 sensor, witch if "open or blown" would give a false code. I checked the fuses and they are good. There is a relay, but the fuse is before the relay, so I doubt it's bad.

I took an educated guess as to witch O2 sensor was faulty. There are in fact four sensors, and front and rear banks on the on the exhaust. Since the code read bank 2 sensor 1, I figured bank 2 as the rear, and sensor 1 as the 1st sensor on the manifold before the cat.
Also, if one goes out, it's probably a safe bet that the other one isn't to far behind.
Replacing the sensor wasn't to hard to do, unplug and a 22mm wrench.

The two pre-cat sensors are a little different, the only difference is the length of wires coming off the sensor, the sensor and the plug are the same. I bought the one with the longer wires so i can swap them if changed the wrong one.

Hopefully I got the right one....
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2002 Wrangler Apex
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Welfare recipients should pass a drug test to get paid…

02' Apex Edition,
2" BB, 31" BFG AT's
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T.O.W. Vehicle
Member


Joined: 15 Jun 2004
Location: Summerville, SC

PostPosted: Sun Sep 20, 2009 4:57 pm    Post subject: Reply with quote

Checking the fuses are a good suggestion, but if it is blown, "WHY" needs to be answered.

Could be (mine was) the wiring harness that runs under the fuse panel and out the bottom between the metal legs that hold it to the fender. The metal legs was rubbing and cutting/grounding the wire causing a false alarm.

Well for awhile anyway. Soon after rewrapping the harness with some heavy duty plastic and tapping it I blew the sensor next anyway.

Check that fuse and repair that wire if necessary. If all that fails look at replacing the sensor! Piece of cake job just take your time with the connector. There is a red locking tab that needs to be removed before pulling the connectors apart...

Best to ya!
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TJ Apex
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Joined: 29 Jul 2005
Location: Mountains of SoCal. 6257 elev.

PostPosted: Sun Sep 20, 2009 8:24 pm    Post subject: Reply with quote

Thanks for the response.
I did replace the sensor, and cleared the code, but the next day the check engine light came back on.
The sensors are the O.E. and have 196,000 on them and needed to be replaced anyway. I will replace the front sensor soon.
I does run a little smoother, and some of the mileage came back.

Thanks again.
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2002 Wrangler Apex
Why do I have to press one for English?!
Welfare recipients should pass a drug test to get paid…

02' Apex Edition,
2" BB, 31" BFG AT's
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T.O.W. Vehicle
Member


Joined: 15 Jun 2004
Location: Summerville, SC

PostPosted: Mon Sep 21, 2009 3:02 am    Post subject: Reply with quote

TJ Apex wrote:
Thanks for the response.
I did replace the sensor, and cleared the code, but the next day the check engine light came back on.
The sensors are the O.E. and have 196,000 on them and needed to be replaced anyway. I will replace the front sensor soon.
I does run a little smoother, and some of the mileage came back.

Thanks again.


I presume you checked the wiring harness then? It is a bundle of wires running from under the PCM(?) (where the fuses are located) and out toward the battery.

It will take some time to pull back the corragated plastic / tape and inspect all the wires. Really, though the outside one are the real suspect. I had to re-insulate a couple (electrical tape) and then re-sheild the bundle with some extra heavy duty plastic.

I cut a portion of a milk bottle side out, cut to fit, and wrapped the bundle and plastic with plenty of electrical tape.

I had three wires that were rubbing the metal legs of the stand, so I know, down the road, this has/will save me hours of trouble shooting someday on a trail.

Good luck with your project!
_________________
"T.O.W. "= Tent On Wheels.
BFG 33" Yukon 4.10 gears w/ locker
Best Top Sailcloth RAT
Warn X8000i winch, Warn Rock Bumpers
RE 4.5"Super Flex Lift
AA HD SYE
JKS Quicker Disconnects
Shrockguards
Tellico & Windrock Tested & Customized!!!!
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TJ Apex
Member


Joined: 29 Jul 2005
Location: Mountains of SoCal. 6257 elev.

PostPosted: Mon Sep 21, 2009 7:04 am    Post subject: Reply with quote

Yes, I did check the harness after your post, and every thing looks is fine.

One thing I did discover is the rubber hose that connects the air intake tube to the valve cover was split, and was dripping oil. I replaced it with steel braided hose I had lying around.

Thanks for the help.
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2002 Wrangler Apex
Why do I have to press one for English?!
Welfare recipients should pass a drug test to get paid…

02' Apex Edition,
2" BB, 31" BFG AT's
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Texas Gypse
Member


Joined: 19 Nov 2009
Location: Rockwall, TX

PostPosted: Tue Dec 08, 2009 12:59 pm    Post subject: Reply with quote

Is everything seem to be running normal now, kinda interested in the subject, due to the fact my O2 Sensor went out not too long ago... according to the scanners at Autozone.

But back to the same problem you had, which was figuring out which one it is.

shock

Texas Gypsy
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T.O.W. Vehicle
Member


Joined: 15 Jun 2004
Location: Summerville, SC

PostPosted: Tue Dec 08, 2009 5:38 pm    Post subject: Reply with quote

Texas Gypse wrote:
Is everything seem to be running normal now, kinda interested in the subject, due to the fact my O2 Sensor went out not too long ago... according to the scanners at Autozone.

But back to the same problem you had, which was figuring out which one it is.

shock

Texas Gypsy


The number of O2 sensors you have depend on several issues concerning the enviromental emmisons setup of your engine.

If you will do a ignition test (cycle the ignition 3 times) the codes you get on the odoimeter will signify what sensor is the culprit.

The codes will look like P0152
Described as Sensor 2/2 2/1 or 1/2 2/1 but I can't remember now which number is the bank and what number is the sensor.
_________________
"T.O.W. "= Tent On Wheels.
BFG 33" Yukon 4.10 gears w/ locker
Best Top Sailcloth RAT
Warn X8000i winch, Warn Rock Bumpers
RE 4.5"Super Flex Lift
AA HD SYE
JKS Quicker Disconnects
Shrockguards
Tellico & Windrock Tested & Customized!!!!
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