S600 TT - the dreaded P0410 code (and the fix)
My '03 S600 was throwing a Check Engine Light. I didn't like seeing that because I prefer to keep my cars in good repair. Additionally, that's an automatic failure during the annual inspection, for those who live in areas where they do that (e. g. California).
I may not live in California anymore, but still, time to do something about this. I don't like broken stuff on my cars.
STAR Diagnostics showed a "current and stored" P0410 code, which refers to the Secondary Air Injection function chain. And what, pray-tell, is this "Secondary Air Injection"? Well, it's a hack that M-B did to try to make their emissions numbers look better when the engine's cold. It's an electric air pump that blows air into the exhaust, right before the catalytic converter, to try to heat up said converter sooner, so that it's more efficient sooner. It sounds just like a Dyson hand dryer, or a hyperactive vacuum cleaner, and it goes on for maybe 30 to 60 seconds. The M-B-specific code for this P0410 fault code is P2003.
STAR Diagnostics also showed codes P0443, P0444, and P0445 as a combined stored code. The M-B-specific code for that is P2026.
Clearing the Check Engine Light would work for maybe 20-50 miles. Then, it would come right back on, all nice 'n' yellow-orange. So, obviously this is a current problem that needs to be fixed.
I tried activating the pump via STAR. Yep, it came on, with that nice, loud whine. Dyson, beware! :-) So, clearly, the Secondary Air Pump was fine. Good thing, too, 'cause that thing's EXPENSIVE.
So, I next tried activating the Purge Control Valve from within STAR (this is component Y58/1 in the STAR diagram). When activated, it's supposed to click a lot. Sure enough, I could both see and feel it clickin' away like a cricket. Looks like that's working, too.
HOWEVER...I noticed something else as well!
When you activate the Secondary Air Pump, there are a couple of sensor voltages--I'm guessing the oxygen sensors--that were hanging around 700 to 800 millivolts (mv). They're supposed to go down to below 40 mv within 60 seconds. Well, THEY WEREN'T!! They were alternating between 93 mv and close to 800 mv, each one of 'em. That's not supposed to happen when this air pump is on. Since the pump's working just fine, then clearly either there's something wrong with *both* sensors...or perhaps there's something wrong with the Purge Control Valve that's supposed to activate when you turn on the Secondary Air Pump. Sure, it's a-clickin' like it's supposed to...but is it really working? Or is there a fault inside of it?
So, figuring one component will go out faster than two, I installed a new Purge Control Valve into this V-12 and tried STAR again. The part cost me $70 online, shipped.
LIKE MAGIC IT WAS....
The voltages are now reading 9 to 10 mv, both sensors, when the Secondary Air Pump gets activated. Turn it off, and it goes right back to 700 to 800 mv. The Check Engine Light does not turn on anymore. And I'm now being more enviro-greenie! :-)
I'd post the pics that I took, but my phone doesn't want to cooperate. If I can get it to cooperate, I will post the relevant pics.
STAR Diagnostics is a Very Good Thing. It can usually tell you exactly what's wrong. If it can't do that, like in this case, it can point you in the right direction with a little bit of thought on your part. Who knows how much this would've cost me at even an independent shop, let alone the dealership?
When you wish upon a STAR...
Saving money, yes you are...!
2000 S430 (Dad's car, used for special occasions)
2000 S500 (wife's DD: my first W220 project car)
2003 S600 ("sex on wheels"--second w220 project car)
2003 S430 (one of two current DD's--third W220 project car)
2005 E320 CDI (the other current DD--first W211 project car)