All four O2 sensors lean
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Joined: Feb 2017
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From: Baltimore County, MD
'13 s212 63 p30. '06 LX470
Occasionally (usually on a long highway drive) my '14 3.5 will throw a CEL and when I scan it, there are always four codes corresponding to all four O2 sensors detecting a lean condition. I doubt all four O2 sensors are going bad simultaneously, so ideas as to what's causing it? It's not frequent or predictable, only happened 2-3 times and honestly I just cleared it out and never even wrote the codes down. I would think maybe HPFP but that would throw other codes that would make it easy. No other codes apart from the four lean sensors.
Any thoughts?
Thanks,
Darel
Any thoughts?
Thanks,
Darel
Thread Starter
Super Member
Joined: Apr 2017
Posts: 518
Likes: 76
From: Mountaintop, PA
'14 W212 Sport, '52 MG TD, '21 Jeep Gladiator Rubicon
Thanks guys. This looks like a royal PITA I may have to pay someone to do. The damn connectors are up on top of the transmission, I can't even see them.
Thread Starter
Super Member
Joined: Apr 2017
Posts: 518
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From: Mountaintop, PA
'14 W212 Sport, '52 MG TD, '21 Jeep Gladiator Rubicon
I find it odd that this started happening right after I replaced my Bank 2 cam phasers. Is there any chance I left a sensor unplugged or a vacuum line off? I would think if something was unplugged I'd get a very specific code for that one sensor, and it would be on all the time, vs. occasional fuel related ones, but you never know.
Is the general consensus that my 12 year old, 185,000 mile car is just due for new O2 sensors? I'll bite the bullet and just pay a shop to change them but before I drop $700 I'd at least like a bit of a warm fuzzy that this is the right way to go. Especially since I'm going to be selling the car in a couple months when my wife's new car comes in, and I'm really only doing it because I want to be a good seller and not dump off my CELs on someone, not because I want to get ANOTHER 185,000 miles out of it.
Is the general consensus that my 12 year old, 185,000 mile car is just due for new O2 sensors? I'll bite the bullet and just pay a shop to change them but before I drop $700 I'd at least like a bit of a warm fuzzy that this is the right way to go. Especially since I'm going to be selling the car in a couple months when my wife's new car comes in, and I'm really only doing it because I want to be a good seller and not dump off my CELs on someone, not because I want to get ANOTHER 185,000 miles out of it.
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Joined: Feb 2017
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From: Baltimore County, MD
'13 s212 63 p30. '06 LX470
If using xentry, you’d get a specific code as well as a diagnostics procedure to track down the issue.
yes it’s could be a coincidence but it could also be the timing was out and now all the sensors need to readjust, or those sensors are dead due to running it out of spec for whatever period.
yes the connectors are hard but not impossible. Just did my e63 a few months ago. A pain, but doable and money well saved.
yes it’s could be a coincidence but it could also be the timing was out and now all the sensors need to readjust, or those sensors are dead due to running it out of spec for whatever period.
yes the connectors are hard but not impossible. Just did my e63 a few months ago. A pain, but doable and money well saved.
Out Of Control!!
Joined: Apr 2019
Posts: 11,962
Likes: 6,803
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
engine combustion faults
I find it odd that this started happening right after I replaced my Bank 2 cam phasers. Is there any chance I left a sensor unplugged or a vacuum line off? I would think if something was unplugged I'd get a very specific code for that one sensor, and it would be on all the time, vs. occasional fuel related ones, but you never know.
Is the general consensus that my 12 year old, 185,000 mile car is just due for new O2 sensors? I'll bite the bullet and just pay a shop to change them but before I drop $700 I'd at least like a bit of a warm fuzzy that this is the right way to go. Especially since I'm going to be selling the car in a couple months when my wife's new car comes in, and I'm really only doing it because I want to be a good seller and not dump off my CELs on someone, not because I want to get ANOTHER 185,000 miles out of it.
Is the general consensus that my 12 year old, 185,000 mile car is just due for new O2 sensors? I'll bite the bullet and just pay a shop to change them but before I drop $700 I'd at least like a bit of a warm fuzzy that this is the right way to go. Especially since I'm going to be selling the car in a couple months when my wife's new car comes in, and I'm really only doing it because I want to be a good seller and not dump off my CELs on someone, not because I want to get ANOTHER 185,000 miles out of it.
It's fair to consider 185kMi old sensors
ECU would be quick to pop a CEL on failed sensors. Without that fault, you can trust what your upstreams Lambdas are reporting:
LEAN OR RICH... Go from there!
(Forget downstreams until they are the only thing left)
Personally I got lost with conflicting data to suspect ECU. A possibility given hot location.
++++ KISS: Dirty old fuel tank...
part of uour onput sound like you may be dealing with bad old fuel... top off with fresh premium gas then read all fault codes since your scanner has limitations with live data.
Last edited by CaliBenzDriver; Dec 1, 2025 at 12:23 PM.
Thread Starter
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Joined: Apr 2017
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From: Mountaintop, PA
'14 W212 Sport, '52 MG TD, '21 Jeep Gladiator Rubicon
Today's codes include Bank 2 sensor 1 stuck rich, bank 2 sensor 2 stuck lean, bank 2 circuit 2 low voltage. First time I have seen a low voltage fault.
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From: Baltimore County, MD
'13 s212 63 p30. '06 LX470
Yes, oil can wick to o2 sensors and the ecu as well as all the other spots you read about. You do not want to be lucky enough to get a code because of this because that would mean it's very wet. Have you checked the harness, thats a five minute procedure to check what you can see on the engine and ecu. Checking the o2 sensors is just as hard as replacing them.
Cali, fun fact. I drive a mint condition 100 series at 260+ thousand miles and recently changed out coils, spark plugs, and o2 sensors and everything that came out looked to be original. No codes or anything but I bought it years ago with 223k so it was time in my schedule to do, since I did lots of other little projects over the years with that first. The other 100 I bought first and still maintain for my partner is the same way, though with habit too much rust for me. The quality difference in the older Toyota parts is insane. I love that old truck.
Out Of Control!!
Joined: Apr 2019
Posts: 11,962
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
After I read this post I reread the thread to see if you had checked the harness for oil and I see you asked the question and nobody answered.
Yes, oil can wick to o2 sensors and the ecu as well as all the other spots you read about. You do not want to be lucky enough to get a code because of this because that would mean it's very wet. Have you checked the harness, thats a five minute procedure to check what you can see on the engine and ecu. Checking the o2 sensors is just as hard as replacing them.
Cali, fun fact. I drive a mint condition 100 series at 260+ thousand miles and recently changed out coils, spark plugs, and o2 sensors and everything that came out looked to be original. No codes or anything but I bought it years ago with 223k so it was time in my schedule to do, since I did lots of other little projects over the years with that first. The other 100 I bought first and still maintain for my partner is the same way, though with habit too much rust for me. The quality difference in the older Toyota parts is insane. I love that old truck.
Yes, oil can wick to o2 sensors and the ecu as well as all the other spots you read about. You do not want to be lucky enough to get a code because of this because that would mean it's very wet. Have you checked the harness, thats a five minute procedure to check what you can see on the engine and ecu. Checking the o2 sensors is just as hard as replacing them.
Cali, fun fact. I drive a mint condition 100 series at 260+ thousand miles and recently changed out coils, spark plugs, and o2 sensors and everything that came out looked to be original. No codes or anything but I bought it years ago with 223k so it was time in my schedule to do, since I did lots of other little projects over the years with that first. The other 100 I bought first and still maintain for my partner is the same way, though with habit too much rust for me. The quality difference in the older Toyota parts is insane. I love that old truck.
wet lambda leans out the fuel trim then super lean engine makes downstream complain of lean.
You are very lucky with your 100'series sensors lasting over 260kMi. They must have been lazy for a long-long time.
I am planning on replacing both my upstream Lambda around 100kMi, not waiting for a faulty sensor heater code.
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MBWorld Fanatic!
Joined: Feb 2017
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From: Baltimore County, MD
'13 s212 63 p30. '06 LX470
I think you got this figured out:
wet lambda leans out the fuel trim then super lean engine makes downstream complain of lean.
You are very lucky with your 100'series sensors lasting over 260kMi. They must have been lazy for a long-long time.
I am planning on replacing both my upstream Lambda around 100kMi, not waiting for a faulty sensor heater code.
wet lambda leans out the fuel trim then super lean engine makes downstream complain of lean.
You are very lucky with your 100'series sensors lasting over 260kMi. They must have been lazy for a long-long time.
I am planning on replacing both my upstream Lambda around 100kMi, not waiting for a faulty sensor heater code.
Out Of Control!!
Joined: Apr 2019
Posts: 11,962
Likes: 6,803
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
oily lambda connector ??
As Balti. pointed out you, may simply be dealing with oily upstream lambda.
Inspect "oil in harness" at these locations :
- CPS Bk1 + Bk2
- ECU M-Connector
- Lambda upstream
Fingers crossed 🤞
Last edited by CaliBenzDriver; Dec 1, 2025 at 09:53 PM.
Thread Starter
Super Member
Joined: Apr 2017
Posts: 518
Likes: 76
From: Mountaintop, PA
'14 W212 Sport, '52 MG TD, '21 Jeep Gladiator Rubicon
When I did the cam phasers in August I had inspected them and everything was dry (I had to pull the ECU at the time). This issue started right after that job was done. I'll check again because it's easy but at this point I doubt oil is the issue.
I will probably pay my local guy to replace the O2 sensors and if that doesn't fix the issue, well, at that point I'll trade it in with a CEL in a few months. Trade in value is $1900 for this car, which sucks because of how much I've sweated and bled for this car for over ten years, but it is what it is. I guess if I do fix the O2 issue I'll try to private party it, but even then it's only worth maybe $5k so not worth me throwing money at the issue.
BANK 2 HAS STILL NEVER GONE INTO CLOSED LOOP. Forgot to mention that. Never once. Bank 1 I'm not really seeing issues, it goes into CL as the engine gets warm and will read "CL-fault" when there's a code showing; goes back to CL when I clear it. No issues there.
This is also the first time I'm seeing the electrical/voltage fault. This makes me feel a little better zeroing in on the O2 sensors.
Going to be a few weeks before I can get this done. Thanks for the help guys. Anything I'm missing, please let me know.
I will probably pay my local guy to replace the O2 sensors and if that doesn't fix the issue, well, at that point I'll trade it in with a CEL in a few months. Trade in value is $1900 for this car, which sucks because of how much I've sweated and bled for this car for over ten years, but it is what it is. I guess if I do fix the O2 issue I'll try to private party it, but even then it's only worth maybe $5k so not worth me throwing money at the issue.
BANK 2 HAS STILL NEVER GONE INTO CLOSED LOOP. Forgot to mention that. Never once. Bank 1 I'm not really seeing issues, it goes into CL as the engine gets warm and will read "CL-fault" when there's a code showing; goes back to CL when I clear it. No issues there.
This is also the first time I'm seeing the electrical/voltage fault. This makes me feel a little better zeroing in on the O2 sensors.
Going to be a few weeks before I can get this done. Thanks for the help guys. Anything I'm missing, please let me know.
