My trusty 2004 Ram 5.7 1500 is giving me intermittent code messages about O2 sensor bank1 sensor 2. The truck is sporting 225,000km at this point.
I have not changed any O2 sensors on this truck in my time of ownership over the past 120,000km.
The truck is only saying code on the one sensor. It is running great. Super smooth and reliable. There are no drivability or performance concerns.

Question: do I replace just the one sensor the truck wants or should I do all 4 of them at the same time? The easy answer is to say replace them all. If that is your answer, back it up and say why.

 

Generally the manufacturer designs the engine management system to be pretty good at detecting variances in sensor performance by comparing sensors against each other, so often replacing the sensor its complaining about takes care of the engine light. However there are situations where the system isn't sophisticated enough to figure out the problem, and just throws a code on the sensor that is showing abnormal readings. In that second situation, you'll waste your time and $ replacing the sensor.

So you can start throwing parts at the problem, hoping to get lucky. Or you can go through a diagnosis process that identifies the root cause.

I recommend root cause diagnosis. There are many videos out there that will show you how to understand the basics of the engine management control system, how it makes air/fuel ratio decisions, quick tests to understand the situation at hand, and ultimately identify the real root cause of the problem.

Here is one of my favorites. He explains the concepts pretty well, and you can make alot of progress with a $15 bluetooth OBD2 adapter and TorquePro app on your cell phone.

 

Thanks for the link. I will check out the video.
I have a BlueDriver reader/scanner.

 

the rear 02 sensors are not used for fuel metering so if one of the rear go bad...it won't cause driveability problems. the rear 02 sensors are used to monitor catalytic converter function.

If diagnostics leads to a failed rear sensor...replace just the bad one. if you get a p0420 or p0430 shortly after rear 02 replacement....you need to replace the front 02 sensor as well.

 

Further information. I do not use the truck alot, but do use it regularly.
Combined town/highway fuel economy is running in range of 12 to 21 mpg depending on when I last reset, the road terrain/conditions, how heavy the pedal was, or if a stint of towing is thrown in. I have absolutely no performance or drivability concerns. Best running truck in the household fleet at the moment.

This code P0137 comes in off and on as a "pending". Sometimes it goes aways, sometimes is sets as confirmed. Another code P0420 also shows up once in awhile but is pretty rare, maybe once in 6 months. I have basically been ignoring this for the last 3 to 4 years. In other words this is not a new code or new problem.

Each fall I go through each vehicle and do the checkover before onset of real winter.
Maintenance already done recently. Done as a matter of my standard practice. Nothing was/is wrong or different with the way the truck was running before or afterwards.
- IAT / Air charge inlet air temperature sensor checked and cleaned, CRC spray electric parts cleaner
- MAP manifold pressure sensor checked and cleaned, CRC spray electric parts cleaner.
- (there is no MAF unit anywhere on the inlet system on this truck. I believe it uses MAP/IAT and the O2 feedback to tune itself)
- Throttle body removed and thoroughly cleaned front/back
- new air filter, stock intake system no mods
- PCV removed and cleaned
- spark plugs are 1 year old, perhaps 8k on them
- new exhaust manifold gaskets and bolts 1 year old.
- exhaust system is original, tight, no leaks anywhere
- magnaflow at the back, basically where the oem muffler was. No other changes.

As I was going through some other basics on the Ram over the weekend, I was thinking about the O2 code and maybe it is time to address the lingering issue. 75$ for the one sensor, give/take. 280$ to do all 4. Cost of sensors only, doing myself; labour is free.

For technical data available right now. There is a screen shot of the code that periodically pops up on the BlueDriver scan tool. I will also soon upload the log files from the scanner. If someone here has charting capabilities and diagnostic experience perhaps they could get it to represent graphically. Everyone can learn some basics from this dataset example and the experts can tell us if and where there is an issue or not. You can work with the original CSV files, the spreadsheet imports, or the PDF. Do whatever you will with them.

In advance ... Thank you for your insights, support, suggestions, comments.

 

Here is the log file from the drive this morning. Some idling, some about town, some flat highway, some hills rivers bridges. Let me know what you think.
I have little experience interpreting the engine runtime data logs such as this. Plenty of experience looking at chemical/manufacturing processes data though.
Superficially, what I see in the log is:
.... the B1S1 B2S1 STFT sensors short term fuel trims generally oscillating +7% to -7%, sometimes tighter spread sometimes higher spread. I believe this is to some extent normal intentional swings made by the PCM and expected ?
.... B1S2 has tendency to drop out to 0 v. It seems to be working fine most of the time but suddenly cuts out to zero here and there and snaps back. I have been under the truck and checked wiring. Pigtial and connector are in good condition. Nothing is obvious.
.... I did notice that the B1S2 B2S2 LTFT sensors long term fuel trims are always negative value. The LTFT range seems to be 0 to -14%, generally in oscillating -3% to -10%. Goes to a much higher -24% when full off the throttle going down a hill. It never ever shows a positive value, always negative. I believe this means the PCM thinks the outlet is a rich condition most of the time and wants to cut back ?

Does any of the data in the log or my brief comments give a sense of direction of what to look at or inspect closer? Do I do nothing, do I replace just B1S2, do I .... ?

...

 

The data in the pdf file isn't labeled for what each column is...... makes it hard to interpret.

 

LOL, not sure why it truncated like that. It could be a limitation of the PDF viewer being used or or the export function of Apple Numbers program I used to create it. When I open the origin PDF it works fine. I made just a couple basic charts to get a feel for it. The charts are not from the scanner. Me doing basic spreadsheet stuff.

ACCESS TO DATALOG FILES:
Maybe this will help. I just tossed the files, in different formats, to a google drive that I have turned on sharing. Anyone and everyone, should have access to see, comment, edit there. Freely look and do what you will with them.
https://drive.google.com/drive/folde...lz?usp=sharing

.

 

Here are pictures of the MAP and IAT sensors that are in the truck right now. Cleaned them last weekend.
Interesting observation at the time. The manifold port for the MAP has bolt stems on either side of it that appears to be for the type of sensor that has bolt through lugs. This MAP that is in there right now does not have the bolt-thrus.

 

Bank one sensor two is shorted. Voltage should range from 0 to 1 volt. Yours appears to be fixed at 1.27. I would expect replacing the sensor should solve it.