Hi,

I've got a check engine light on. After scanning with OBDII I got P2A00 and P2414, sensor exhaust sample error bank 1 sensor 1, and sensor circuit range performance bank. The sensor data showed:

Oxygen Sensor Output Voltage (B1-S2): 0.890V.
Oxygen Sensor Output Voltage (B2-S2): 0.595V.
Oxygen Sensor Current (B1-S1): 1.93mA
Oxygen Sensor Current (B2-S1): 0.00 mA.

Do you know what the problem might be? As I understand, 0.890V is very rich, the norm is around 0.45V, right? But that is for B1-S2. What should the normal current value be for B1-S1 and B2-S1?

Is this a bad sensor or an upstream exhaust leak? How can I check? Would it be a good idea to swap left and right upstream sensors and see if the problem is following the sensor?

Thanks.

 

Can you see the voltage for B1S1? Mine fluctuates between 0.1V to 0.7ish Volts. This is for both B1S1 and B2S1.

For B1S2 and B2S2, mine stays around 0.735V.

Unfortunately my car scanner does not give me current readings for the O2 sensors, only voltage.

Swapping them is a good idea. Doesn't cost you anything.

What is your year and mileage? I have an 05 E320 with the M112 engine. I replaced all the O2 sensors earlier this year with new Bosch O2 sensors. They were not too expensive and it was easy to replace.

Also just fyi, for those that have Secondary Air. When the pump runs, you can see the B1 sensor readings drop down to roughly 0.015V as air is blown over the O2 sensor. If the pump is running and the O2 readings do not go down, that most likely means you have a clogged Secondary Air passage.

 

You can just change out the upstream sensors. As mentioned above, the downstream ones don't really do much and don't really get worn out. They normally look at clean exhaust and don't switch much. It's the upstream that are always switching and get worn out by raw exhaust. If the converters are working right, the downstream only see clean exhaust and don't switch much so they don't wear out. When the upstream and downstream have the same numbers, it means the converters are shot. You probably can't swap them because the length of the wires are different which is why when you buy them they specify upstream or downstream. Rockauto has the Walker upstream sensors on clearance for about $50 each, don't forget to use the 5% off code you can find on retailmenot.com. I put those in a while ago and they seem fine, I only changed them out because I was over 100k and figured it was time.

 

Hi
i have a mercedes c350 2012 coupe
i did it catless and muffler delete then i tuned it at project A after making it catless check engine light turned put it on scanner it showed that oxygen sensor 1 bank 1 has an electrical fault and im not feeling that my car gained extra hp. If i changed the oxygen sensor does the check engine light turns off and hain the hp?

 

Hi F1Fan and cetialpha5,
Thanks for the replies and great suggestions. I was just about to record waveforms (sine waves) from upstream sensors and swap the sensors, but the check engine light went off. I drove the car around the block and the light did not come back. I guess, I should not try to fix it if it ain't broken...I'll wait and see if the light comes on again.
The car is 2008 E350 4matic, 97K miles. Sensors are probably original.
I don't understand what my scanner shows. I can't see voltages of B1S1 and B2S1. Both upstream sensors (S1) show current in mA. Both downstream sensors show voltage in mV. What should these values be? I can't find any specs in the WIS too. Do you know? Thanks. I don't think they have secondary air.
Thanks for mentioning Rockauto too. It looks like the OEM upstream sensor is ~$250. That is expensive.

 

What was the error code you were getting with the check engine light? I would just replace the upstream sensors, they don't last forever. If you listen to the people who make them, they say ever 50-60k but usually they're gone in the 100-150k range. You can get them to last longer, but you get slightly better gas mileage with new O2 sensors because they switch faster than old tired ones so even if it's not giving you a code, it's still worth changing out the upstream sensors. At $100 for the pair of Walker ones, it was a no brainer for me to do them.

 

I actually felt slightly better engine performance after changing out all the O2 sensors. I had the original ones in there until 153k miles. Gas mileage now is as good as it was when the car was new.

 

The check engine light is off, but something is wrong with the driver's side exhaust. I did some tests. Please take a look and help me figure out the problem.
I started with cold car, warmed it up to ~430C cat temps (a few minutes on idle), got these readings:



B1S1 current seems high. Then I started looking at the waveforms.
B1S1 on idle:

B1S1 at 1500 rpm:

B1S1 starting with 1500 rpm and then releasing gas pedal to 700 rpm idle:

B2S1 idle:

B2S1 1500 rpm:

B2S1 1500 rpm drop to idle:

B1S2 idle:

B1S2 1500 rpm:

B1S2 1500 rpm drop to idle:

B2S2 idle:

B2S2 1500 rpm:

B2S2 1500 rpm drop to idle:


Then I decided to try to clear error codes. It did not work. I still have problems on the driver side:




At this point I turned off the car, and then decided to check the values again. After waiting a bit again until the Cats were at about 450C I read the values and got very different readings. Here is the summary screen:

B1S2 voltage seems to be very low. Then I recorded waveforms again.
B1S1:

B2S1:

B1S2:

B2S2:


It looks like B1S1 current is consistently higher than B2S1 current. On a second test B1S2 voltage seems to be very low, typically below 0.1V. There is more smoke coming from the driver's side tailpipe, more noticeable at 1500 rpm.

Does this look like a bad oxygen sensor B1S1 or some other problem? Maybe the sensor is just doing its job and sending correct values, but the problem is elsewhere? How do I know from these tests that catalytic converters are working properly? On the second test the B1S2 voltage (0.065V) is 10 times lower than B2S2 voltage (0.665V). So, something is definitely wrong.

The next step, I guess, is to swap the upstream sensors and see if these readings follow the sensor.

 

You have a problem with the upstream sensor. Just replace the one sensor. You're supposed to use antiseize on the threads when installing them and it's not easy to get them out. It's also possible the wiring is damaged as it doesn't look like you're getting a reading. A vacuum leak could also throw it off. These things are hard to diagnose online, you have to go in and look at it. You should just replace them instead of playing around by swapping it, then you're swapping it back or putting in another one. They're not that easy to replace. Had to use a few zip ties to hold the wiring in place.

 

Which sensor are you talking about saying I am not getting a reading?

 

When I changed the plugs on M112 engine, it was real easy. S1 pre-cat sensors, was accessed from underneath the car. It is close to the catalytic converter so I recommend doing this when everything is cold. 400+ degrees, C or F is no joke! The S2 post-cat sensors also reachable from underneath. All of the wires for O2 sensors were routed to a bracket to keep it away from hot exhaust. I used an O2 sensor socket to remove it, but you could probably do it using a regular socket wrench. But a caveat here, if you live in a place that rusts cars easily, I would suggest using the proper O2 socket tool. Just fyi, the Bosch O2 sensors come with anti-sieze already on the threads so all you need to do is screw them on. I did see Walker brand O2 sensors for a bit less money, but the price difference was not that big. For example, $75 vs $60. Your situation may be different, you may have a different engine etc.

 

I have M272 engine. The cheapest OEMs I found are $230 each shipped (mbpartsource, part # 003 542 71 18). That is $460 for a pair. And it is not clear whether it will solve the problem, as it could be vacuum leak, exhaust leak, coolant leak, or many other things. I can replace just 1 sensor, but then I have one "old and tired" sensor. Wouldn't this cause misbalance? Bosches are $180 each from Pelican Parts. Walkers from Rockauto are way cheaper, just $50 each. I am in a southeastern Mass, so a lot of rust.
Do you know what is tripping the error code? What is out of spec for B1S1 in the graphs above? Is there a document that says what the specs should be? Thanks.

 

I put in those Walker O2 sensors, just a tad over 110k and I figured it was time. No issues with them so far. Also in MA, wasn't that easy for my indy to do them but they did come out with the O2 socket. Replace both of them, you're overdue anyway. The error code basically says you have a bad oxygen sensor or an exhaust leak. No one can diagnose an exhaust leak online. You have to get in there and look around. Wiring could also be damaged as you're not getting a good signal. Basically if you look up the error code, a P2414 is a bad connection or exhaust leak. Disconnect the old one and clean the contacts if you don't want to spend any money, but if the oxygen sensor is bad or the connector is bad, you're going to have to do the job twice. Wouldn't waste too much time trying to diagnose it, you risk cooking the cats while you play around with it and you should look at the price of new cats.

 

Thank you for all the replies. Your feedback is really helping me.
I did a few more tests. Visually, I don't see any exhaust leaks around exhaust manifolds and near both gaskets. Inspecting them is tough, though, even with a mirror.
Here is my fuel trim:


My long term fuel trim is 7.8% for both banks. I believe, the norm is below 10%. My short term trim, however, is only working for bank 2. For bank 1 it stays at 0.0%
The scanner reports Fuel System 1 Status: OL Fault. This, I believe, is Open Loop Fault, which means there is no valid feedback.

The B1S2 and B2S2 voltages are reasonable and near-constant, as they should be, but my B1S1 lambda is 1.999, which is erratic. Should be very close to 1.000

Here are the two lambdas side-by-side. So, B2S1 is working and B1S1 is not.


The current reported by the B1S1 sensor is 2 orders of magnitude higher than the current from B2S1 sensor:

This all suggest that this is the problem with upstream bank 1 oxygen sensor, which is probably short.

Would you agree? Do you think anything else except the sensor could cause these readings?
Also, my guess is that the car at this point just discards the erratic readings from bank 1 and uses some pre-programmed tabulated values to adjust A/F mixture. Right?
Is bank 1 sensor 1 located on passenger side?
Thanks.

 

Just wanted to thank you for helping me with this issue. It was a bad oxygen sensor. Now all fixed!
I rented both oxygen sensor wrenches from Autozone (OEM 57162 and 57110). The job can be done without the clawfoot wrench, but the other one was really helpful. There is very little room to turn the handle near the catalytic converter. I used large wrench as an extender for the handle. The hardest part was unscrewing the existing sensor, but it was not too bad. I only used ramps under front wheels, no jacks or stands, so it was pretty tight underneath.
To diagnose the issue it helped to look at the short term fuel trim and confirm that bank 1 was always showing 0.0 and that there was a close loop (CL) fault error code.
I was 99% sure that bank 1 sensor 1 is passenger side, but to confirm it I unplugged it first and then started the car. As expected, I've got an additional error code for bank 1 sensor 1 heat element malfunction. Then I had my morning coffee for 20 minutes waiting for exhaust to cool off
Installing the sensor is very easy. Now both lambdas are close to 1.000 as they should be.
It took me a bit to figure out how to clear the error codes. I have icarsoft MB v2.0. The codes can only be read with the engine running. Instructions say to put the key in the ON position with the engine OFF to clear the codes. That did not work at first. Then I tried to clear the codes while the engine was running. At some point the check engine light went off, but the error codes still stayed.
Then I realized that to clean the codes I need to get out of the OBD check engine menu all the way to the top menu, then do smart scan or manual scan and manually go into the ECM unit. Sure enough, the codes disappeared after clearing from the ECM.
Some people complained that icarsoft cannot reset SRS. At least my version worked just fine on my neighbor's Sprinter for resetting the airbag light (he disconnected the airbag, but forgot to disconnect the battery).
Runs great now!

 

Glad everything worked out for you! Now you have some data to know if other sensors start acting weird later.

Most important part: The morning coffee!

 

Hi everyone, I need help please!

My 2012 E350 has a code P0051 which is B2S1 sensor, my mechanic even replaced both B2S1 and B1S1 with Bosch OEM ones, but I still haven’t been able to erase the error code, and as soon as I start the car, the engine light pops back on. I have no idea what the issue really is.
I have the exact same icarsoft scanner, when I tried to erase the code from ECM, it says clear error code unsuccessfully.

I ran live data on it, the oxygen value shows -0.02mA. I already attached 2 pics on here, can anyone help me out please? I appreciate it!

 

Did you look up the cause of a P0051? It's basically a bad oxygen sensor, wiring problem, blown fuse or ECM problem. Looks like you eliminated bad O2 sensor by replacing it, but you probably have to check the wiring or ECM.

https://www.fixdapp.com/blog/p0051-code/

 

How do I find out if it’s the other issues tho? I actually took my car to a mechanic shop, they told me it was bad communication between the 2 upstream sensors, and I already replaced both of them.

 

When trying to clear codes with icarsoft make sure you get out of the OBD check engine menu and go into the ECU unit menu. Then clear the codes. Clearing these codes from check engine menu does not work.

 

I have already tried that, couldn’t even erase that thru ECM, it says “clear error code unsuccessfully”

 

The code you get is for the problem with B2S1 (driver side front). The snapshot you posted above is for B1S1. I had a problem with B1S1. The good sensor B2S1 showed very small current (at idle), like 0.03mA and lambda was to 1.01. The damaged sensor B1S1 was showing lambda of 2 and current of 2.02 mA.
Look at the short term fuel trim for both banks (see my screenshot). Both numbers should change when you play with gas pedal. If one stays at 0.0% it means data from that sensor is not coming to the computer (for whatever reason). But I think both my heating circuits were good.

Now, your code is for the heating circuit. I recall you can see both temps in icarsoft in real time. You should see both temps rise to 400 something degrees in real time with icarsoft when you start the car (over like 30 seconds)

If you are sure that sensors are good, I would check the heater fuse and wiring next.

 

Actually I replaced both B1S1 and B2S1. And both show the same oxygen value -0.02mA.

both new sensors were good, but they coulda been burnt out again if there was a wiring issue.

how do I replace the heater fuse and wiring?