O2 sensor question

[GlenwoodCJ7]

Well, your white wires will be your heater wires, the gray will be your ground, and the black is your signal wire to your ecm. When your engine is warmed up, you should get .01-.09v on the signal wire. You are showing 4.14-4.13 signal. I would double check with the mfg of your sensor to validate those numbers as their sensors might be a little different.

A few other things to look at... all of which can show o2 sensor defective

Overall system voltage
Coolant sensor
TPS
MAP sensor

 

[TerryMason]

I'm still fighting this after all this time. I'm trying to get serious about this, and collect my thoughts.

I'm still getting a P0161, which appears to be an O2 heater control error.

I've cut the ends off an old O2 sensor, and compared the readings from what my computer says is bad (2/2) to the 1/2 sensor, which isn't throwing a code. The readings are pretty much the same, which surprised me. I expected the heater control signal to be off.

O2 Sensor color	Harness color 2/2	Pin	Function	Voltage
Black	Brown / Gray	1	Heater Control	4.13 (can go 5 to 8v)
White	Black / Lt Blue	2	Ground	Common / Ground
Gray	Blue	3	O2 Return	2.51
White	Brown	4	Signal	4.14mv (can go 7-10mv)

My manual references a relay in the PDC, but I can't find any relay with any type of O2 heater control reference.

 

[Mtpockets]

The black wire is the sensing voltage and should have a mv signal from .1 to .9mv. I noticed you were reading 4.17 V on the black wire. That is too much. The O2 sensor should output between .4-.6mv at normal operating temp. An O2 sensor doesn't begin outputting a signal until it reaches the neighbor hood of 600*. manufacturers began putting heaters on them so they start working sooner after the engine starts. Is it possible that you have the heater voltage on the black (sensor voltage)? When you made the repairs on the wiring harness they may have gotten crossed. White should be 12 V + through heater and back to ground on the other white. Gray ground and Black O2 sensor voltage back to PCM.
disconnect the sensor, turn key on and see if you can locate which white has 12v. Test the other white to ground to determine correct connections.

 

[TerryMason]

It's possible that I'm doing something wrong but in my testing none of the wires are providing 12v, not even on my working sensors


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[Mtpockets]

Is the sensor you're having problems with down stream of the catalyst? The pre catalyst sensor(s) are closer to the exhaust manifold/header and probably heating up and working within the programmed time in the PCM and the post Catalyst sensor is not. Usually there will be a huge temp drop across the Catalyst. I think I would search out why there is no heater voltage at any sensor if this is the case. I know this driving you crazy, it would me too.

 

[JPNinPA]

Check for an exhaust leak.
Also your CAT may have gotten damaged and fallen apart like mine. All I found was an empty CAT.



JPNinPA
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[Mtpockets]

I have been thinking about your problem and read through your post again. You said you are getting error code P0161: O2 Sensor Heater Circuit (Bank 2 Sensor 2) and another post mentioned code 0058 heater circuit high error I believe. With these codes I am inclined to think your issue is going to be somewhere in the heater circuit not necessarily with the sensor. All 4 wires were mashed and shorted so there would almost have to be a fuse or relay out not allowing voltage to the heater circuit, since you aren't finding it on the other sensor(s) either. As you know without seeing things for yourself it's hard to troubleshoot problems so I hope I am offering up logical solutions that help.

 

[JPNinPA]

Good point! Is it possible your fix of the mashed wires create a delta in resistance that keeps the reading outside the spec? Either high or low.


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[TerryMason]

Check for an exhaust leak.

I "blew it up" with my air gun (wrapped duct tape around the tailpipe. No leaks that I can find.

I have been thinking about your problem and read through your post again. You said you are getting error code P0161: O2 Sensor Heater Circuit (Bank 2 Sensor 2) and another post mentioned code 0058 heater circuit high error I believe. With these codes I am inclined to think your issue is going to be somewhere in the heater circuit not necessarily with the sensor. All 4 wires were mashed and shorted so there would almost have to be a fuse or relay out not allowing voltage to the heater circuit, since you aren't finding it on the other sensor(s) either.

Originally my problem was that my 2/2 sensor's wires were pinched between the body and trans after a hard landing. I was getting an 0058 at the time. I found two of the harness wires cut, and the other two worn. I reconnected everything with butt connectors, and then got the P0161 message. I've replaced the o2 sensor with factory, and again with NGK. I've pulled the butt connectors, and soldered the connection, using heat shrink tubing.

I found this info on another site:

According to the Powertrain book the P0161 is a heater fault. When the O2 sensor is stone cold it is like an open circuit. There is a 5v supply in the PCM that goes through an internal 2 Megaohm resistor. The PCM watches how fast the 5v drops and it uses that information to determine if the PTC heater is working.
Set condition is "O2 sensor volts stays above 3v for 75 seconds."

I know that other year TJs have an O2 Sensor heater relay. From what I understand, my model uses the ASD relay for these heaters. I'm not 100% on this yet. I swapped the ASD relay with another and had no change.

I'm going to devote some more time to this this week and see what I can figure out.

 

[Mtpockets]

You will get it figured out I'm sure. Keep us posted on what you find for the fix. I am curious to know what is causing your problem.

 

[JPNinPA]

If you do 3-5 warm starts does it go away?

Have you hooked up to see the O2 switching?


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[TerryMason]

If you do 3-5 warm starts does it go away?

Have you hooked up to see the O2 switching?

It's been burning into my dash for 2 years now. It's not going away anytime soon. Always the same error, that the O2 heater circuit failed.

I'm not sure what you mean by O2 switching though.

 

[JPNinPA]

Sry by switching I mean waveforms...

No cylinder 6 exhaust leak? There is bolts that loosens on 4.0 TJs causing leaks.




.

Regards,
JPNinPA

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[RAVEN13xxx]

Terry, If you fixed the wiring without replacing the sensor, chances are you blow the heater element of the sensor itself. Now the the wiring is repaired, I'd replace the sensor i'd throw an OEM sensor in it.

 

[98Chero]

SteelHeadz "or a battery disconnect to clear the PCM"
SteelHeadz brought this up at the start of your thread. did you disconnect the battery for 12 to 24 hours. My mail man told me about this trick to clear codes and lights etc...

 

[JPNinPA]

SteelHeadz "or a battery disconnect to clear the PCM"
SteelHeadz brought this up at the start of your thread. did you disconnect the battery for 12 to 24 hours. My mail man told me about this trick to clear codes and lights etc...

FYI it doesn't have to be that long. 2min.is long enough. I usually disconnect the positive terminal and turn the key to the ON position to drain any charge. Then hook it back up. Codes cleared.


Regards,
JPNinPA

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[TerryMason]

Terry, If you fixed the wiring without replacing the sensor, chances are you blow the heater element of the sensor itself. Now the the wiring is repaired, I'd replace the sensor i'd throw an OEM sensor in it.

Hey Raven13xxx, long time no see! I had the same hope, and I just replaced it (using a Denso, not OEM with the same result. I may revisit that with an OEM

SteelHeadz brought this up at the start of your thread. did you disconnect the battery for 12 to 24 hours. My mail man told me about this trick to clear codes and lights etc...

I've reset it using a scan tool, which I believe would accomplish the same thing.

No cylinder 6 exhaust leak? There is bolts that loosens on 4.0 TJs causing leaks.

The error code says that the 2/2 O2 heater circuit failed to pass the test. My understanding is that the sensor is working, but the heater isn't.



At this point I'm going to revisit the wiring, and probably redo that. There's really not much more that it could be. My problem is that it's really hard to get to - it's on the back of the engine, by the firewall.