O2 Sensor Idle Voltage

[jeep_boss]

TL;DR - does anyone know what the idle or bias voltage should be on an 05-06 TJ Rubicon for the upstream O2 sensors? (Bank 1, sensor 1 and bank 2, sensor 1).

Reason that I ask - I have had sporadic P0132 and P0152 O2 sensor codes fire this last 4-5 weeks resulting in momentary limp mode, and overall unoptimized engine operation.

Tonight, on a hunch, I decided to check a couple of areas of my engine wiring and I have pinpointed within ~2-3" of where the issue is. Simply put - I can manipulate the voltage readings, decreasing voltage from 1.27V to ~0.81 by lightly squeeing a suspected faulty area of the wiring run.

If anyone knows off hand (doubtful, but I'm theowing a hail mary) or if anyone has an OBDII reader that can tell me what the idle voltage for these sensors read, I'd be endebted!!!

 

[ac_]

Here is a pretty good write up I used when tracing my 02 issues

http://troubleshootmyvehicle.com/jeep/4.0L/how-to-test-the-oxygen-sensor-1

See if that helps

 

[jeep_boss]

Here is a pretty good write up I used when tracing my 02 issues

http://troubleshootmyvehicle.com/jeep/4.0L/how-to-test-the-oxygen-sensor-1

See if that helps

That's an impressive write up man, I definitely appreciate it! Here's my peoblem though - I replaced all 4 O2 sensors with the correct NTK sensors a few weeks ago, along with my exhaust manifold. I had been getting similar O2 sensor codes, which went away immediately after the replacement.

I suspect that wiring may have been damaged right before hand, when I was doing some other work to my Jeep in the area where I can make the voltage drop by gently squeezing that wiring bundle. If my theory is correct, I may have temporarily fixed the issue when I buttoned everything back up (eg. placed the wiring harness in such a way that it could have corrected a physical wiring short maybe).

I am trying to wrap my head around this problem with the information that I just digested from your write up. Something is happening with the voltage to the two sensors i question, when I do that. I can reproduce it 100% of the time as well.

Any thoughts?

 

[jeep_boss]

Took a 30 minute test drive with my OBDII reader plugged in. Both upstream sensors were stuck at 1.27V, while both downstream sensors were operating with variable voltages (0.1-0.9V). CEL is still illuminated.

I am wondering for testing purposes, if should have repositioned the wiring harness in such a way that the voltage for both upstream sensors were in the sub 1V range. This is new territory for me, but it seriously sucks.

 

[ac_]

My issue ended up being a bad ground on the back side of the pigtail of sensor one bank one. Go through the write up and take all of the readings with a volt/ohm meter. It sucks but in the world of auto electronics the best thing you can do is learn your multimeter. Somewhere on this forum we have a PDF version of a service manual for your jeep. Go through that write up step by step, and it will walk you through your problem I bet. Start at page one and work your way back and let me know if you get stuck. My first suggestion though is my jeep only had two 02's and didn't go through the fuse, but I read somewhere that your 4 02 does go through a fuse so first thing first check all of your fuses! Then download the manual for a wiring diagram and then follow the write up, but after the 4x4 swap meet tomorrow.

 

[jeep_boss]

My issue ended up being a bad ground on the back side of the pigtail of sensor one bank one. Go through the write up and take all of the readings with a volt/ohm meter. It sucks but in the world of auto electronics the best thing you can do is learn your multimeter. Somewhere on this forum we have a PDF version of a service manual for your jeep. Go through that write up step by step, and it will walk you through your problem I bet. Start at page one and work your way back and let me know if you get stuck. My first suggestion though is my jeep only had two 02's and didn't go through the fuse, but I read somewhere that your 4 02 does go through a fuse so first thing first check all of your fuses! Then download the manual for a wiring diagram and then follow the write up, but after the 4x4 swap meet tomorrow.

I'm comfortable with my multimeter and electronics . I've soldered my fair share of aftermarket PCUs to factory ECUs, plus I'm not colorblind / so I can trust myself a little ;-). I knew my O2S's didn't have a relay, but I did not know that they were fused! Tomorrow, I'll definitely start checking the diagrams and go as far as backprobing the PCM if I have to. My intuition leads me to think that I will have to lay a new wire, the bend in the factory harness containing the O2S wires is a huge concern. I shouldn't be able to manipulate both upstream voltages by touching the wire bundle!

I need sleep - didn't realize until just now that it is daylight savings time tonight. Puyallup is an hour and change down the road :\

Thanks again man, Psyched for tomorrow. Will let you know how it goes! Cheers

 

[jeep_boss]

I monitored my 2 upstream sensors today while driving down south the that swap meet event. Eventually, the voltage would drop below 1.27 to the normal operating thresholds (both upstreams were bouncing up and down for Lambda).

What I find strange is that they were only dipping below the static 1.27V at certain times while I was driving. I need to try and better understand what they should be doing, I am led to believe that they should be a tive like that once they have heated - but I need to dive in where I left off last night to grok their operating parameters.

The downstream sensors were a tive almost immediately (if not immediately). I also scored a better OBD tool from one of our better local pawn shops on my way back from the swap meet today. So far it has been great!

 

[jeep_boss]

I have the problem sorted out now. An area of my wiring (where that hellacious plastic bridge at the rear of the motor - at the end of the valve cover) had some wear. I fixed the insulationnon the affected wires (one happened to be my HO2S ground), and I rewrapped the section along with the remaining wire runs that weren't protected very well with good quality split loom and tape.

The only janky thing here is that I am using a heavier duty pair of zip ties to support the wire harness, but meh - it is solid and it works.

The upstream sensors are working properly and things are looking good :thumbsup:

 

[ac_]

I have the problem sorted out now. An area of my wiring (where that hellacious plastic bridge at the rear of the motor - at the end of the valve cover) had some wear. I fixed the insulationnon the affected wires (one happened to be my HO2S ground), and I rewrapped the section along with the remaining wire runs that weren't protected very well with good quality split loom and tape.

The only janky thing here is that I am using a heavier duty pair of zip ties to support the wire harness, but meh - it is solid and it works.

The upstream sensors are working properly and things are looking good :thumbsup:

Good Job! That was sort of my same issue.

Also just to let you know the heater part of you 02 circuit is only for start up and only for a few seconds. It is sort of there to fake out your computer to make it think your exhaust is hotter than it is. It basically gives your exhaust time to heat up on its own. You know how fast your exhaust heats up.

 

[jeep_boss]

Good Job! That was sort of my same issue.

Also just to let you know the heater part of you 02 circuit is only for start up and only for a few seconds. It is sort of there to fake out your computer to make it think your exhaust is hotter than it is. It basically gives your exhaust time to heat up on its own. You know how fast your exhaust heats up.

I remember reading about that on a Chrysler O2S troubleshooting page somewhere. Fortunately, those were the only wires that looked to have had some slight wear.

The plastic bridge at the rear of the motor is starting to make sense now. I guess the engineers realized the extreme heat temps that are produced that exposes the wire bundle to it, which can cause some sagging (making heat exposure even worse in the lower wire section near the mini cats). That area gets frigging hot.

The plastic bridge is a crappy design though, I could not take mine apart without breaking it. I looked at the big picture yesterday and chose to support and protect the wires better, and then I tied it to the last fuel injector support bolt towards the rear of the intake. It is not perfect, but the wires are far less exposed now to the raw heat coming from the headers and cats.

 

[ac_]

I remember reading about that on a Chrysler O2S troubleshooting page somewhere. Fortunately, those were the only wires that looked to have had some slight wear.

The plastic bridge at the rear of the motor is starting to make sense now. I guess the engineers realized the extreme heat temps that are produced that exposes the wire bundle to it, which can cause some sagging (making heat exposure even worse in the lower wire section near the mini cats). That area gets frigging hot.

The plastic bridge is a crappy design though, I could not take mine apart without breaking it. I looked at the big picture yesterday and chose to support and protect the wires better, and then I tied it to the last fuel injector support bolt towards the rear of the intake. It is not perfect, but the wires are far less exposed now to the raw heat coming from the headers and cats.

Nice work!

 

[jeep_boss]

Nice work!

Thanks! It runs a lot better now at least

 

[Mick's Jeep]

I monitored my 2 upstream sensors today while driving down south the that swap meet event. Eventually, the voltage would drop below 1.27 to the normal operating thresholds (both upstreams were bouncing up and down for Lambda).

What I find strange is that they were only dipping below the static 1.27V at certain times while I was driving. I need to try and better understand what they should be doing, I am led to believe that they should be a tive like that once they have heated - but I need to dive in where I left off last night to grok their operating parameters.

The downstream sensors were a tive almost immediately (if not immediately). I also scored a better OBD tool from one of our better local pawn shops on my way back from the swap meet today. So far it has been great!

View attachment 34874 View attachment 34875

Hi, we have bought a jeep wrangler TJ 1998, and are experiencing the issue that the O2 sensor reading Bank 1 S1 stays at 1.000V, S2 almost immediately working.
If S1 suddenly decides to start working, it jumps up above 1V, making the engine stutter, running rich, shaking etc. As soon as the value “settles” or after a restart, the engine behaves normal again.
We have replaced O2 sensor but these problems persist, sounding like your experience.
Any advice as on where to start?
No fault codes given on the OBD scanner.
Thanks in advance.

 

[GoldenGorilla]

As far as I am aware, all the NTK sensors have a range from 0-1V and they don't actually go all the way to 1.0V - Except that Chrysler decided on startup to measure the warm up function indirectly by running higher voltage through the sensor resistance side to make sure they warm up and the voltage drops in the time expected. I have an 04 with 4 sensors and have not been able to catch the peak warmup voltage on the 2 upstream sensors in a log file, but they go to 4.5V or 5V briefly to ensure that the heaters are working and open the resistance.

Once the resistance drop is verified, the sensors will go into their normal operating mode which will bounce around alot and typically be a bit rich during warmup oscillating between 0.882v and 0.030v. Once the vehicle is warm the expected voltage will settle on and average 0.490v.

It sounds like you might have an issue in the wiring harness either with the heater circuit or the sensor circuit and you'll need to trace those pins for continuity back to the PCM.

 

[Mick's Jeep]

As far as I am aware, all the NTK sensors have a range from 0-1V and they don't actually go all the way to 1.0V - Except that Chrysler decided on startup to measure the warm up function indirectly by running higher voltage through the sensor resistance side to make sure they warm up and the voltage drops in the time expected. I have an 04 with 4 sensors and have not been able to catch the peak warmup voltage on the 2 upstream sensors in a log file, but they go to 4.5V or 5V briefly to ensure that the heaters are working and open the resistance.

Once the resistance drop is verified, the sensors will go into their normal operating mode which will bounce around alot and typically be a bit rich during warmup oscillating between 0.882v and 0.030v. Once the vehicle is warm the expected voltage will settle on and average 0.490v.

It sounds like you might have an issue in the wiring harness either with the heater circuit or the sensor circuit and you'll need to trace those pins for continuity back to the PCM.

Hi, thanks! Just to be sure we're checking the the right things: should we measure continuity of the sensor circuit between the pin on the connector (harness side) of the O2 sensor and the corresponding number on the PCM connector?
Same with the heater circuit?

Should we also measure the connector (harness side) of the O2 sensor while connected to PCM (with key in contact to see voltages)? And which pins should we measure (see picture below)?

 

[GoldenGorilla]

You'll need the pin diagram for the harness at the pcm too. Of course ground pin to ground continuity is important and can be the source of a fault. But you'll be wanting to check for not necessarily continuity, but something other than infinite resistance between the O2 signal pin and pins other than it's own on the PCM side.