Originally Posted by
BrianBrave
I went through the exact same issues as you this summer, except I purchased a new RCM from the MB dealer and had the air pump rebuild by local shop that does starters/alternators etc.. only thing I did different was not replacing my EGR valve.
Air pump would run every morning like clockwork, tested with the engine cold by applying voltage to pump and actuator and could feel air blowing out the exhaust.
Two days later, the code would comeback.
Then, every morning for a week - before starting the engine, I would switch on the rear window defroster and what-do-you-know, the problem went away and I passed CA smog.
I'm guessing that the ECU monitor for the secondary air pump would see enough current draw to calculate that the air pump was switching on.
Been about 3 months now without using the rear window defroster trick and no issues.
Hope this helps.
4/1/2019
OK, I had the same problem for quite a while on my 2004 coupe. Last weekend I unplugged the lead to the air pump (front if the engine, right on top. You should see TWO pins marked + and - in tiny little symbols). I briefly attached jumper wires from the battery to the smog pump. It ran fine, so now I know that is good.
Tonight I first removed the negative (black) cable from the battery, then unplugged the ECU (passenger side near the back of the motor, move plastic sliding locks, 5 or 6 multi pin plugs, one 40A fuse - see photos some posted here on this page) from the car, then CAREFULLY pried the plastic back cover off (use 2 or 3 flat screwdrivers and be sure they don't damage anything inside). Then I am looking at the 5 (or so) mounted relays. The one furthest toward the back of the car is for the smog pump (4 pin plug). CAREFULLY remove the tiny little spring from the relay and DON"T drop it or LOSE IT or you're toast. Move the little copper cable (that holds the square contact plate on) up and over the corner so that you can pull the little contact plate back out of its little slots and pull it out away from the relay with the copper cable still intact. This will allow you to take a look at the tiny little contact plate electrodes. Mine were all black and burnt, but otherwise is fairly good shape. Take a SMALL nail file with fine sand paper on it (maybe 200 grit or higher) and CAREFULLY and lightly sand and smooth and clean both the slot (inner electrode) and the other electrode on the little plate. Don't remove any electrode, just clean them up and give them a smooth surface - doesn't take much sanding. GENTLY reassembly the relay putting the little spring back on and be sure it holds the relay in the OPEN position (just like the others). Reassemble and reinstall the ECU unit in the car. Put your battery cable back on (this will have reset your Check Engine light). Start the (awesome) Crossfire up and be blown away at how awesome runs now. Note... no more engine light. Repair cost: $0.00 plus 20 minutes of light labor. This worked great for me. If it helps you, just send me lots of your money (hey, the mechanic would have got it anyway, right?).
If you still get the 0410 code after doing this you'll probably need a new ECM, ( OR I'll give you $75 for the whole car... if it doesn't have any rust... if you can deliver to my house in Ohio :-} ).
I sincerely hope this helps lots of people avoid an expensive repair for this simple issue. Bad on you MB, but really once you've been in there once, its a really easy fix.