2005 TJ O2 sensor and exhaust question

[ROGLSTUBB]

Its been years since I have been on this forum (sold my zj's 6 years ago) but I figured out my password and I have a quick question. I am considering buying a 2005 TJ with a 4.0. Somebody but a banks monster exhaust and I am thinking they bypassed the o2 sensors. It looks like they have the CEL light out of the dash and when I pulled codes I got four different ones.

Is this a common modification or did somebody just to a poor job on this. I don't mind fixing it right if thats what it takes. Just been out of the loop on jeeps.

 

[JPNinPA]

What codes do you have? If they did bypass the O2 sensors then yes you will have CEL codes. if not based on the codes you could narrow it down.

 

[ROGLSTUBB]

Sorry I don't remember exact codes. But I believe they were o2 sensor heater circuit malfunction. On the chevy's I have had in the last few years there was a fuse caused this code. I checked the owners manual to see if it could be similar but I did find anything.

I checked autozone website and it looks like there are 4 o2 sensors. I haven't actually crawled under there to see if they are still there. They seem reasonably priced if they are needed.

I generally like my CEL functional so if I get the jeep I will probably fix so that it does. Just mainly asking if this is "common" modification.

As now I am thinking about it I should be looking for the catyltic converter as well. Perhaps this is why they messed with o2 sensors

 

[Catoctin Jeep]

To pull your codes up again you do not need a code reader. Turn your ignition off and on three times within 5 seconds or so and the codes will appear on the odometer. When all codes have been displayed "done" will appear on the odometer. You may have already known this.
The Banks exhaust should be 50 states compliant, therefore all o2 sensors should remain in the stock location. My guess would be that they were never hooked back up or reinstalled in the wrong location. Upstream, downstream. If that is the case, yes you will get the dreaded CEL.

 

[ROGLSTUBB]

I actually did not know that had changed to the odometer. I was figuring since CEL was out the code reader was the way I would have to check.

So here are the codes
Po 135, 141, 155, 161

 

[Catoctin Jeep]

I just checked the codes and all come up as heater failure for one and two sensor. My guess is that the plugs are damaged when reinstalled or one of the wires were melted on the exhaust. Was the exhaust replaced from the engine back or just after the cat. The reason I am asking because there was a point when the new exhaust systems were coming out for these Jeeps and were throwing off the o2 sensors. This maybe the case. I am not sure what the fix was. If you could get the kit number from the owner you could call Banks and asked them if this is normal. But the flag is the heater issue. Just check all the wires and make sure they are in good condition first and go from there.

 

[ROGLSTUBB]

I just took a better look at the underneath. It looks like stock exhaust all the way back to muffler. All four o2 sensors are in place I did not see a damage to the wires or harnesses.

Is there a fuse or a relay that controls the heater circuit to them?

 

[JPNinPA]

O2sensors are known to fail and so do the mini cats. Only put OEM sensors in as other brands cause issues or inconsistent codes. The cat back ic a common mod I have the Banks Cat Back and Borla headders. I also had some bad o2 sensors and a failing cat bank 2.

Yes there is a fuse.

 

[ROGLSTUBB]

I went ahead and bought it. Would someone mind telling me what fuse control the o2 sensors. I will get the manual for it on payday. Just curious if could be it being all four sensors throwing a cose

 

[JPNinPA]

On calif emission vehicles the PDB under the hood uses a 20A fuse in #17. Behind the glovebox Is a 10A in Slot 18.

 

[ROGLSTUBB]

Ok checked all fuses everything was good. Examined all four o2 sensors and either the car lot I bought the jeep from or PO detailed the sensors or replaced them. They are exceptionally clean. I bought a Haynes manual to check into the 02 sensor heater circuit. The electrical diagram in the book only shows a two 02 sensor setup so it's pretty useless. I was able to find a diagram of the o2 sensor itself online and found the two white wires are for the heater. I checked for 12v at the wiring harness with it running and get nothing. So I am pretty sure this is my problem.

So does somebody maybe have a better diagram of the four o2 sensor setup?

 

[southtj]

Not sure if this will help but this is the best I could do from my 04 factory service manual. Click on them to make bigger.

 

[ROGLSTUBB]

I don't think that will work for me. The part numbers for o2 sensors are different from 2004 to 2005. I read online that somebody had a similar problem on a 05 and ended up being ECC. I am starting to think maybe computer controls heater circuits on 2005 and 2006 as they are the same part number 02 sensor.

Anybody have a FSM for an 05 or 06 can confirm this. Possibly give me some pinouts on the computer to check wiring

 

[ROGLSTUBB]

Just wanted to update this thread with some new info. I bought a FSM online for the 05 TJ and my suspicions were correct the computer on this year controls the voltage to the O2 sensor heaters. I checked the pin outs on computer and I am getting less than a volt to the heater circuits. My best guess is it is the computer that is bad. Just weird everything else would work on it. I will post again when I finally correct the issue

 

[TerryMason]

I know that I'm bumping a super old thread, but did you ever get a fix to this problem? I've got the exact same thing - one of my O2 heaters is failing, and I've verified that I have continuity all the way from the sensor to the computer.