LoFox

Hi Everyone,

I have a 2010 C63 and this year was the first mandatory SMOG check to renew my California registration. I believe as a new procedure for SMOG testing in CA the sniffer is no longer used and a pass/fail is entirely based on OBD2 results which mean no CEL and ALL supported readiness check must be complete.

In my case I have no stored code, but my O2 and O2 Heater readiness check never complete (all other are ready.) From searching around it seems that this is somewhat common in aftermarket ECU tunes but my car has not had anything aftermarket flashed, additionally I also had an MB dealer re-flash the ECU just in case as part of attempting to fix the problem but it didn't do anything.

Next I attempted to change the O2 sensors to rule out any issue with them (although I imagine I would have a CEL if the O2s were really at fault.) So far I ended up changing 3 of the 4 O2 sensors but it has not changes the results in any way. (I haven't changed the passenger side pre-cat sensor, it's a b**ch to get to.)

As overall driving distance does play a factor in ODB2 readiness check, I've driven ~300 miles since the initial re-flash at MB till now post O2 sensor change. At this point, other than changing the 4th O2 sensor I have no idea what else to do, I'm open to any suggestion and any solutions, especially if someone has heard of an issue similar to this. From other posts on the forums I've read some unsubstantiated claims that it is possible to force(?) the ODB2 check to be complete through an aftermarket flash (this was mentioned once or twice by some users discussing EuroCharged ECU tuning) but I have no idea if its true.

Again, any help that you can offer is greatly appreciated!

abcut973

I was thinking "drive the car for 2 full cycles". But I assume 300 miles would suffice
Is it a car that you daily drive? Or occasionally?
Are you the first owner?

LoFox

The car is driven daily in most cases and at minimum 5x per week, typically just to work and back ~15-20min. Since trying to fix this issue I've been taking it out for longer drives to try to meet the drive cycle requirements though. I'm not the first owner so I can't be sure what was done to the car before, but I did buy it from an MB dealer rather than private party (not sure if they would take additional steps to make sure it's in proper order)

Lastly, I'm ~90% sure that at some point in the past (~2-3 years ago maybe) I plugged in my ODB2 scanner, just for fun, and it must have returned all readiness checks passed because otherwise I would have started looking into the issue at that time, especially since it was under warranty.

hachiroku

from what i've seen on other cars...O2 readiness usually occurs within 35 minutes of driving.

anything evap or emissions related on the intake side will need to occur upon cold start or full operating temp.

again...these assumptions are for most cars, not specifically Mercedes.

LoFox

Yeah that's been my experience in the past too. All other readiness checks are complete, several completed within ~20 minutes of driving after the ECU reflash at MB and the final (minus o2 and oh) completed after 1-2 days (probably cold-start related)

hachiroku

if you still are having O2 readiness checks incomplete i would proceed to complete a wiring to ECU test. either the sensors are faulty or you're having an issue with communication to ECU.

you never know...one of the pins to my airmatic computer for the W211 snapped on its own. ECU has never been touched and it took me 6 months to figure it out. basically fried my airmatic computer and found the issue months after when i was installing my electronic lowering module.

LoFox

That's a very good point, I will need to do research on how to actually test the wiring to that extent as I imagine paying a shop or MB would cost a small fortune due to typical per/hour rates, I don't think it will be quick. (Next I'd like to replace the final O2 upstream sensor since I have a spare and that should rule out any issues with the sensors themselves)

I took care of SMOG so it's good to not have that hanging over my head now and I can take my time trying to actually fix this issue. I'll post updates if I ever figure out what is wrong, it might help other in the future if they have a similar issue.