I have read so many postings on this issue on the CLK's, C230 ect. on the 4 cylinder but have not come across anything on the 3.2 V6 as this doesn't have the cronic issues as the other W203's. The air pump runs fine in the mourning, then shuts off as it should. I have changed the check valve, air pump changeover valve; erased code and it returns a few days later. This system doesn't appear to be complicated and I have ruled out the air pump and relay as they appear to be working fine. No water in the air pump and it works as it should. Don't know what else it coud be. Am I ruling out air pump and relay too early? Please help I am stumped. I also cleaned out the combination valves. Just a little bit of carbon buildup. I haven't checked them for blockage at the intake manifold though. Should this be next? Thanks for any kind of help I give up Tim

 

yes dont rule out the relay...change it, its cheap....since the air pump is running it should be ok, but before you go any further swap in a new relay

 

Thanks for the reply. I ordered the relay as it was real cheap. I am wondering about the little check valve. It doesn't make sense to me the direction it's installed and am wondering if it's in backwards. I would think it would be installed to open with the intake manifold vacuum and not closed to it. I reversed it and am waiting to see if it clears the code. Tim

 

Update. Code cleared. Before I purchased my OBD2 code reader, I had an Indy shop diagnose check engine light for a different issue. Must have put the check valve in wrong. Free diagnostic check not worth it. Tim

 

Where is this relay located? I am having the same problem

 

I have a 97 e320 with the same problem. any suggestions? How much is it for this relay?

 

The relay box is located on driver's side all the way against firewall next to brake booster. AboveAllMotorWerks sells them for under $8 but would recomend you buy more items to get the free shipping because shipping is more than the item costs by itself. I think free shipping for $50 and above. I would recommend you change all or at least your two vacuum lines that connect to front of intake manifold. They also sell those. Mine were cracked. Tim

 

Hi I am having the same problem on my CLK 320, my check engine light was on because one of my oxygen sensor went, i had it replaced, then they disconnected the battery to reset the system (this made the light go away). Two weeks later the light comes back one, I thought another one of the 02 Sensors went, but I took it back to have a diagnostic and the P0410 - "Secondary Air Injection Malfunction System Logic Chain" came up!

What does this all mean?

 

Secondary air injection is an electric air pump(smog pump) It only turns on in the mourning when your car is cold for about a minute or so. First you need to check in the mourning and make sure it turns on and off(sounds like a hair dryer) then go from there. Possible common problems are the relay, broken or cracked vacuum lines going to the system, and the check valve. Tim

 

I have a 03 ML320 with a P0410, I have manually checked the air pump and it works fine, the relay and fuse are good but the pump does not come on when I cold crank the engine. Any ideas?