shadi-k

Hello , I keep receiving this message "2031 -no or incorrect CAN message from control unit BCM" , whenever I scan the car , my main issue was misfire , I do not know if this is related , but how can I fix this error , car is S600 2009.
what's a BCM and why I have it with the engine scan?
any thoughts?

BOTUS

within the car industry the acronym BCM has been taken over and used to describe a component Mercedes call a SAM (signal acquisition module). Industry wide its now called a Body Control Module (as in nothing at all to do with way the engine runs)

the old use of BCM on a Merc meant Battery Control Module - and again its almost impossible to cause an engine misfire


however if you have a V12 you will very likely need to spend $7k on a Voltage transformer (VT) and 2 sets of coil packs that probably got damaged when one coil stick (out of 24 on your car) got old and shorted everything out

NOTE: DO NOT replace a coil pack without first fixing the VT - or its highly likely you'll find you just threw $2500 in a skip within a week.



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https://mbworld.org/forums/s-class-w...ml#post8755102

BOTUS

error above oil = old

shadi-k

Thanks for the reply BOTUS , glad to know that the BCM/SAM has nothing to do with the engine although the fault code is 2031 , I believe code has something to do with the engine , I did replace the coils & spark plugs, VT works fine , it worked well for few months and now it's misfiring again , injectors are fine , I'm suspecting the crank case ( PVC) , as I found oil reaching the throttle body from the drivers side, but I'm not sure if this can cause a misfire though!

BOTUS

before randomly posting part of the story - people should check the recent threads (most stuff comes in waves as it all the same age machinery...)


check for puddles as per this for the NON misfire issues - like this yesterday

https://mbworld.org/forums/s-class-w...cal-issue.html

BOTUS

what tool are you reading error codes with - most cheap ones make up garbage if its a powertrain code P2031 Exhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 2),

shadi-k

Thanks you for the reply , I do not know the tool , but the scan was done at a big Mercedes garage , so I assume it's a good tool.
what do you mean by sensor 2 please? is it the one after the Catalytic converter ? i.e. furthest from the engine?

BOTUS

..nearly all ODB2 codes are standardised between all manufacturers - and where say BM or Merc invent further info for their own cars we can have unique additional codes - but that one is a standard one

I don't know enough about the V12 engine management - because its got turbos it might be excited about exhaust temps in ways NA engines aren't (NA = normally aspirated - aka non turbo) - so whilst CAT sensors have heaters (that often die around 10 years) I don't think its these playing up...

Bank 1 should be the right side (when sat in the car) - The left bank is numbered 7 to 12, front to rear. The firing order is 1, 12, 5, 8, 3, 10, 6, 7, 2, 11, 4, 9.


I get this isn't from your's but I expect the senor names could be the same with a similar location - I can't find much about the petrol ones let alone the v12 - but likely a dead sensor that's not to bad to swap...

"Temperature sensor upstream of
turbocharger (B19/11)
The temperature sensor is located on the exhaust
manifold flange upstream of the turbocharger where it
determines the exhaust temperature. This allows the
thermal load on the engine and the turbocharger to be
monitored."

"Temperature sensor upstream of the CAT or diesel
particulate filter is (B19/9)
The temperature sensor is located in the assembly
upstream of the diesel particulate filter (DPF). The
sensor measures the temperature of the exhaust gas
as well as the thermal load on the oxidation catalytic
converter."

shadi-k

I replaced both upstream sensors " ones closer to the engine" , unfortunately no luck same code , thanks

BOTUS

the fault if it is indeed the correct code - P2031 Exhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 2)

and you say now you have changed both ?

as in changed the first ones (that the exhaust gas reaches) on BOTH banks ?
as sensor 2 should be the second sensor further downstream and only the right side is reporting broken (your left as you look in to the engine bay standing by the headlights)

shadi-k

right , I changed the first ones (that the exhaust gas reaches) on BOTH banks , not the ones after the catalytic converter , now I get it , will replace sensor 2 as per your description , will keep you posted

BOTUS

hey - this is the issue with the internet - when you said misfire it doesn't usually come from a canbus issue.... its either or fueling or ignition or mechanical (aka a damaged components or something its not doing something at the correct time - which these days could be either a stretched chain or and electronic device not knowing how to help cam phaser hit the right place)

we don't know what tools you are getting theses codes from - many cheap ones make stuff up... and whilst you can glean some help from the internet on fault codes there are so many manu specific codes its often hard to know what they are talking about.... I just found a more exhaustive list of error codes and found Merc went silly and started to use the same code for multiple different issues..... some of which cross over the original less confusing generic ODB2 standards....


you may have fault P0600

this remote diagnosis started going wrong as most manufacturers very stupidly forget to give the initial systems diagnosis Character - and as most Canbus faults are on body control systems - plus you didn't give the very start or the last part of the fault code it looks like you jumped to changing parts before finding out at much as possible

I just found a Powercontrol fault along the lines of what you posted

P2031 No or incorrect CAN message from control unit N80 (Jacket tube module)(P0600)
P0600 Serial Communication Link Malfunction

BOTUS

that full fault code may well come from a damp puddle under the passenger floor mat

see the link in my post #5 ......

along with another post today that could be 4 cars in one week with a puddle issue !!!!

shadi-k

thank you , you are right I replaced the coil packs , car runs fine , but with the same error message

BOTUS

did u follow the post about V12 fun and games?

just changing a coil pack is very risky (or if you like the risk and soldering just a coil stick), the failed part often damages a voltage transformer (VT) an external box of tricks only on the V12.... it manages the different voltage and switching every spark, that the weird V12 system uses... they frequently get damaged by a single failing coil stick - and can blow up the entire new pack of coils..... plenty of owners find the misfire is back inside a week and the new part is toast....

before this became common knowledge many owners did 2 or 3 - then their brain gets fried and it starts getting expensive

- many wise owners take this route... https://www.v12icpack.com/

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