benzchk

Okay... so I know there has been many posts on this particular code and I've read so many of them that my eyes are about to bleed and still have not been able to find the fix. Here's my story.

I own a 2003 E320 sedan. Recently I have replaced all 4 O2 sensors and along with it had a P0410 code. I replaced the Secondary air pump and it runs normal on a cold start. The code was cleared and about 200 miles in, my check engine light came back on. I took it to the local auto parts store to get a code reading. The suggestion was to replace the relay. My initial thought was, if the relay was bad, wouldn't that cause the air pump to not function? At any rate, for such an inexpensive part, I bought a new one and replaced it. Just a side note, all the parts that I replaced are genuine Mercedes OEM pieces. I also checked the tubing and replaced those just for good measure.

Cleared the code and drove the car for about 3 days and the CEL came back on to my dismay. Had it tested again and it same code came up saying I need a new relay. My car is about to get a SMOG check and I am afraid it won't pass. Any ideas of what else I can do to fix this issue? Thanks!

Plutoe

Regrettably, P0410 is very specific----relay for air pump---there are no if ands or buts, however after changing three relays one would suspect that the pump itself may be the issue!!

benzchk

It's a brand new pump and I do hear it running on a cold start and stops as soon as rpm decreases so about 20 seconds or so. But just for good measure, I tested all 3 relays and they were all good. Could a bad fuse possibly throw this code?

cmriv

egr valve?

benzchk

Wouldn't a bad EGR valve throw it's own code? I might have to take it apart and clean it to see. At this point it's either that or throw in the towel and just get an new car lol. It's hard to let go since I got her brand new and she was my first car. Served me well through the years but the ole girl is finally starting to break down.

Plutoe

Yes an EGR fault has its seperate fault---most folks only read what they want to hear--see post 2 and read words number 3 and 4

Find the seconday air system wiring diagram on startek WIS and begin a test program to find the source of the relay issue!!

cmriv

Not exactly that specific. It could be a generic code like secondary chain malfunction. I understand that you do not have that code however it wouldn't be a bad idea to check anyways.

JoeCross

Mind you, I have the V12TT engine so my configuration will differ slightly, but the theory of operation is the same. Aside from the pump and relay, there is also a 3-way vacuum changeover valve and two vacuum actuated check valves. When I had the P0410 code, I initially replaced only the pump, which I found to be very corroded. The code came back after a few days. Relay tested good. I removed the engine cover and passenger side intercooler and inspected the vacuum lines and valves. I found that one of the vacuum hoses going to the changeover valve was cracked and torn, and the others were loose. I replaced the vacuum hoses and cleaned the large check valves with carb cleaner. These other issues are what allowed moisture to reach the pump to begin with, and cause the corrosion. I have driven the car over 1000 miles since, and have not had any codes pop up.

benzchk

Thanks everyone for your advice. I went through again and checked the vacuum hoses to make sure everything was tight and going where it was supposed to. Apparently one of the hoses came loose and let in moisture to the air pump. When I took the pump apart, there was water present and needless to say the motor was fried. I had to replace the air pump again. Not a cheap fix but so far I've driven it for 600 miles and no CEL so looks like a fix and also passed my emissions test.

George Jubran

How can I check if the relay for 1999 E320 is functionning properly or defective . I got the P0410 code and would like to make sure if the relay is defective or ok before replacing the secondary air pump. Thank you