quik55

Hey guys, I got a check engine light for
p0141-O2 heater circuit (bank 1 sensor 2)
p0156-O2 circuit (bank 2, sensor 2)
p0161-O2 heater circuit (bank 2, sensor 2)

I cleared them and the light stayed off for a 100+ mile drive.

then on my next drive I threw
p0156 and p0161 again.

I would clear and drive and these would come back. Constant p0156 along with either p0161 or p0141 but not all three again…

after doing some research I found that a faulty maf can cause these codes. I first cleaned maf which did not help and then replaced with new Bosch unit.

still received p0141, p0157 or p0156 along with p0161.

I then decided to just go ahead and replace both rear O2 sensors.

p0141 comes back consistently after clearing and then starting car for the 2nd time along with p0156 eventually after some driving.

p0161 has not come back..

confirmed it is not maf by swapping the known to be good one out of my ml55 and same issue.

any ideas? Or similar experience? Not sure what else it could be at this point other than maybe 2 faulty O2 sensors from rock auto?

any other possibilities? Thanks!

quik55

Bit of a fun update…

so I went down the rabbit hole of every possibility it could be minus the maf and O2 sensors themselves…

in the interum I had done the “soft” ecu reset which may have been a bad idea…
ie unplug battery for 30 seconds then reset windows/radio/hvac etc then let run for 5 mins and drive…
it definitely seemed to be relearning and she was shaky for most of that first 5 minutes… it did say it could take a little longer for it to relearn everything.
something new was after driving a little when put into park rpm’s will surge to approx 1500 and hang there until shifted to neutral/drive back to park or turned off…
Hoping that will just take a little for it to figure out on its own…

i then decided to next best bet inspect the wiring to the sensors… low and behold I found that one of the wires had completely broken off..
and did not appear to be repairable.
this wasn’t great but was a bit of a smoking gun…

luckily there was a 430 at my local pick and pull and I was able to get basically the exact socket minus one wire color being different..
i spliced that in and codes for both rear o2’s didn’t immediately return… kinda great!

took her for about a 15 mile drive no codes, but rpm’s did surge to 1500 when put into park.
fillled her up and drove back another 15 miles with no codes appearing.

when putting her in park rpm’s did rise again but leveled out from shifting to nuetral/drive and back to park.

shut her down and checked codes and oh boy!! 😂😂😂 2 new pending ones…

P0170 fuel trim bank 1
P0173 fuel trim bank 2

both funnily enough from search 99% of people say it is 99% of the time bad maf lol

cleared codes and let her sit… maybe just a fluke and rpm’s in park will eventually level out. If not can also be vacuum leak/o2’s so should be fun…

was pretty happy to not have the O2 codes come back for now but hopefully not a new issue has been created.

guess I can only test drive and see what comes up hopefully no others!!!

would really like for her to be healthy and happy especially before winter storage.

she was doing so well right before 195k too…

any opinion on best Mercedes’ centric scan tools that give the best parameters/pinpoint issues?

will see what happens…

quik55

Hopefully the last update to this little saga haha 🤞🏼

went to next most logical step other than maf and while thinking unlikely, checked for vacuum leaks…

Voila…




must have knocked it off last time i was messing with the maf…

adjusted harness and reconnected…
high idle in park gone.
idles smooth runs well. Short drive no codes.

hoping she will stay that way and healthy and happy for more time to come. Another 200k atleast!

also hope that driving with the 02 codes several hundred miles As well as the vacuum leak for a bit didn’t do any damage create any further issues in the future.

i know this thread has basically been for just me at this point but shoutout mbworld and all who have posted in the past which assisted in this specific scenario (not much other than ML’s with weird issues haha)

what a trip looking into replacing cats, ecm star c3,4 or 5 and feeling a bit hopeless.

ironic how it occurred literally right after finishing front brake new caliper rotors and pads. Almost considered it possible to be having installed pad wear sensors which she never had under my ownership 😂

while most if not nearly all threads with my original issues never really had a solid solve… replacing new o2’s with used or others etc hopefully it was just that wire and worst case she has a new maf and rear o2’s.