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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!
The DTC basically tell us that the HEATER portion and its wiring towards the oxy/lambda sensor is the bad dude. CURRENT means it is on-going problem and can not be deleted until you fix the problem.
BASED ON M276 3.5L abd 3.0 turbo as I do not know anything on M272 electrical, The front sensor is not an oxy sensor per se, it is a wideband oxy sensor or better call it a lamda sensor because that is what Xentry calls it.
It is a 6 wire sensor and not a 4 wire one like sensor 2 on both banks. This lambda has a calibration resistor too. Its fast and highly accurate compared to 4 wire oxy sensor.
Assuming the OEM Bosch sensor you use is GOOD and CORRECT, and old sensors replaced with new one still having P0051 , you may suspect the wiring run between the ECM towards the 6 pin lambda sensor is the culprit.
I do not know your engine model, I am only quite familiar with M276 3.5L and my 3.0 turbo, as for wiring information coming out of the ECM, engine computer.
I know there is older version called M272 which is also a 3.5L but I do not know what year W212 will carry it, nor do I know of its ECM wiring or the exact lamda sensor in use.
You best provide your VIN.
I hope your DTC is not a true P0051. If it is true, you may have just burnt out the heater section of your new Lamda/Oxy sensor and so will all new sensors, until you sort out the short circuit.
Here is why............... and I am using M276 3.5L as example. Most cases the wiring design would be similar even for M272 if it is also a 6 wire lambda sensor. Below is similar for my M276 3.0 Turbo too.
Now, the said Lambda sensor is powered by Fuse X at Front SAM and it is always HOT when engine computer wakes up.
So, power always available to fuse X when relay N called Circuit 87 Engine ( relay N powers fuse 22,23,24 & 25 ) , whenever engine computer wakes up and most cases that is including merely opening the car door.
If fuse X has power which is +12V and your short to ground (-12V) is at pink 1 which is at zone 4 green ( Between Pin 80 of engine computer to pin 3 of Lambda sensor ) , that means your heater get turned ON permanently.
This heater is accurately controlled by ECM via ground switching inside the ECM ( not pure chassis ground ) using PWM and it not like water heater being ON a long time. Its very accurately controlled in terms of duration and amperage.
I am attaching Bosch sensor LSU42 narrow band and LSU49 wideband tech manual for your mechanic to do a test on the new and old sensors, to see if the heater section is kapoot or not.
I am also attachning engine computer wiring of M276 3.5L which has these oxy/lambda sensors.
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I can help you in tracking the short circuit if you are keen to learn along side of your mechanic, if you are the curious and DIY type.
If you are the I best use money to repair guy and not interested to learn, by all means make sure your mechanic is a good one electrically.
CAUTION : Do not ever get itchy handed and try to power up the heater using jumper wire direct from battery thinking its like a bulb. DONT'. Special controller does this duty, which is the engine computer.
LSU49
5.4 Electrical heating of the sensor
The sensor heater may never be connected directly to battery voltage. It must always be controlled by the LSU control unit or the vehicle ECU. Heating the sensor before the engine is started is not allowed.
it seems like you are a professional at this, but it’s a little too complicated for me to understand. Basically you are telling me it’s a wiring problem that’s kept and will keep burning out the new sensors i replaced with right?
so I need to fix the wiring issue, not the O2 sensors or ECM, correct?
============== Basically you are telling me it’s a wiring problem that’s kept and will keep burning out the new sensors i replaced with right?
so I need to fix the wiring issue, not the O2 sensors or ECM, correct? ==============
Yes, that is what I gather from the troublecode description and the fact that your new sensor still produce the same troublecode.
As I said, for ur mechanic to verify the NEW sensor condition for its heater burnt out or not , use the Bosch technical document.
Your mechanic should understand the test workflow and finding the heater wire which is "touching" car metal parts aka short circuit to ground.
Oxy/Lambda sensor location is very hostile between exhaust manifold and CAT, it is very hot and if somehow the clip holding the connector to the car body came loose, the connector may dangle closer to the CAT/Sensor and that is crazy hot.
What is your engine model btw ?
============== Basically you are telling me it’s a wiring problem that’s kept and will keep burning out the new sensors i replaced with right?
so I need to fix the wiring issue, not the O2 sensors or ECM, correct? ==============
Yes, that is what I gather from the troublecode description and the fact that your new sensor still produce the same troublecode.
As I said, for ur mechanic to verify the NEW sensor condition for its heater burnt out or not , use the Bosch technical document.
Your mechanic should understand the test workflow and finding the heater wire which is "touching" car metal parts aka short circuit to ground.
Oxy/Lambda sensor location is very hostile between exhaust manifold and CAT, it is very hot and if somehow the clip holding the connector to the car body came loose, the connector may dangle closer to the CAT/Sensor and that is crazy hot.
What is your engine model btw ?
It’s W212. Do you think I need to drive a little longer to complete the full circle for the new sensor to warm up and be functional?
Well, the lambda/oxy sensor to work properly needs to be like 400C and above, in city traffic jam, you won't get this temperature without the heater fast enough.
Heater also handles the condensation during engine start-up in cool/cold weather, where condensation can damage the lambda/oxy sensor portion, the N cells.
With a healthy heater, within like 20 seconds from engine cold start ( 30C ) the lambda/oxy sensor hit 400C+ already, as per my log file below.
U will never get rid of the heater troublecode if you dont fix the on-going problem.
U can never get proper fuel trim with the sensor without a heater. At worse case you can have a rich misfire and damage your cat-converter ...... expensive man .
Simply get your mechanic to read the documents I provided and solve this asap.
Drive safe......
Here is cold start from 27C , engine idle to 3.82 minutes. Top right is CAT-converter temperature which is the Lambda/oxy sensors bank 1 and 2, see how fast to 400C with heater and how linear both sensors are, till we cant see the blue line.
Well, the lambda/oxy sensor to work properly needs to be like 400C and above, in city traffic jam, you won't get this temperature without the heater fast enough.
Heater also handles the condensation during engine start-up in cool/cold weather, where condensation can damage the lambda/oxy sensor portion, the N cells.
With a healthy heater, within like 20 seconds from engine cold start ( 30C ) the lambda/oxy sensor hit 400C+ already, as per my log file below.
U will never get rid of the heater troublecode if you dont fix the on-going problem.
U can never get proper fuel trim with the sensor without a heater. At worse case you can have a rich misfire and damage your cat-converter ...... expensive man .
Simply get your mechanic to read the documents I provided and solve this asap.
Drive safe......
Here is cold start from 27C , engine idle to 3.82 minutes. Top right is CAT-converter temperature which is the Lambda/oxy sensors bank 1 and 2, see how fast to 400C with heater and how linear both sensors are, till we cant see the blue line.
hmmm when you say it needs a heater, what do you imply? I need to replace the heater inside?
Do you think the new sensors are still good at this point or they have been damaged already?
hmmm when you say it needs a heater, what do you imply? I need to replace the heater inside?
You can't replace the heater only, no way. You have to replace the SENSOR unit.
We have to stop playing ping-pong here.
Since you do not understand at all about cars ( which is OK), you can't even ID your engine, where W212 is the model/family designation of E class 2009 to like 2016..... we are having a very tough conversation here.
Do you think the new sensors are still good at this point or they have been damaged already?
I kept telling you to use your mechanic to troubleshoot as per my advice, or take it to official MB workshop, its your call. I have given the Bosch sensor document to reference to.
If you are not helping me by reading slowly and properly what I wrote, you are being selfish/lazy/whatever ....because I tried hard to explain and you kept asking the same thing.
Read...read...read, is that difficult to ask ?
hmmm when you say it needs a heater, what do you imply? I need to replace the heater inside?
You can't replace the heater only, no way. You have to replace the SENSOR unit.
We have to stop playing ping-pong here.
Since you do not understand at all about cars ( which is OK), you can't even ID your engine, where W212 is the model/family designation of E class 2009 to like 2016..... we are having a very tough conversation here.
Do you think the new sensors are still good at this point or they have been damaged already?
I kept telling you to use your mechanic to troubleshoot as per my advice, or take it to official MB workshop, its your call. I have given the Bosch sensor document to reference to.
If you are not helping me by reading slowly and properly what I wrote, you are being selfish/lazy/whatever ....because I tried hard to explain and you kept asking the same thing.
Read...read...read, is that difficult to ask ?
Bro, I appreciate your help, but I don’t think you read what I wrote either, I specifically said in the original post that I’ve already replaced both upstream sensors. And I also already answered you about my vehicle’s ID model which is W212, and you could’ve also already noticed the year make and model from my original post if you read it carefully. No need to be arrogant here, just because you have more knowledge than me in mechanics.
05-14-2022, 03:05 AM
and so will all new sensors, until you sort out the short circuit.
