Hello, first post here. So I was literally going to get an inspection sticker the week my check engine light came, just awful luck. My Benz is a 2010 C300 4matic Sport w204 making 2024 the last year in my state MA that would fail me for an emissions CEL (cars over 15 years can pass with emissions CEL). So I get 1 code P0410 secondary air injection pump.

First thing I check is the fuse and the fuse is blown! Could I have lucked out with just a fuse? I put a new 40 amp Maxi fuse in. My question is now, will my CEL shut off automatically if it is just was the fuse that was faulty and if so, when will the CEL turn off? Do I have to drive it a certain amount of miles? Would unplugging the battery turn the CEL off? Also, if the fuse was blown, should I replace the relay too? What would cause the fuse to blow, is there an underlying problem?
My secondary fan was making a loud jet engine whistle before on cold start but now its not.

Any advise or info would be very helpful. Thanks!

 

If you have a scanner why not clear the code, drive around and see if it comes back on? I dont think disconnecting the battery will reset the code.

The light will turn off if the problem was fixed, not sure how many drive cycles it may take though.

Is the secondary air pump working?

Im in MA and know when you go to get an inspection sticker they can see how long ago codes were cleared, by days i believe. I think as long as the diagnostics say "Ready" and there are no codes youre good to go.

 

I only have a cheap scanner, when I tried to clear it said failed. The CEL did not turn off after changing the fuse. I drove it around today for 30 mins, highway included. I was hoping it would go away as i need a sticker. Maybe a few more driving cycles would work? The pump seems to work, on cold starts in the winter if would make the loud jet engine sound that others mentioned but not all the time. Today it was warm out around 70 and when I started it "cold" for the first time of the day I didn't hear anything loud, Does the secondary pump always turn on for the first start of the day or only when its cold out?

Also the CEL came on the first 80-90 degree day of the year, I wonder if that had something to do with it. How can I clear the code, do I need an expensive scanner? thanks

 

If your inspection sticker is already expired I would just go go it inspected, get the Rejected sticker then deal with whatever the issue is. Im in MA and have recieved many tickets for expired inspection sticker just because im lazy, or used to be about getting it inspected. You can still drive and the retest is free.

The secondary air pump runs for the first minute or so upon cold start to inject air into the exhaust manifold to help with unburned fuel and heats the cats up quicker. Its for emissions purposes. If the car has already been driven and warmed up the air pump isnt needed and will not turn on.

I would verify it is still working. On cold start go and feel the air pump to make sure its operating. You should hear it also, will sound like air being pumped in the manifold.

If you dont have a Mercedes specific scanner I wouldnt try erasing the check engine light codes. Even if you do erase the code the IM readiness testing from the car may not have been completed, if you go get it inspected the machine will say its not ready to be tested and you wont pass.

For the check engine light to turn off a certain drive cycle needs to be performed, so the car can perform its tests. I have no idea what that cycle is though. Ive read its all different things, from driving certain speeds, stopping certain amount of times, starting the car a certain amount of times? Heres something I just came across when searching "Mercedes drive cycle for check engine light to turn off".

 

In searching I came across this info about the drive cycle. Its for another model Mercedes but may be the same for the W204. It mentions the check engine light needs to be off, so maybe try disconnecting the battery for a few minutes. I have never done it so I am not sure. or if there is an Autozone around you that can erase the code, if they do that?

Heres the link to the full page: https://m.smogtips.com/smog-question...-K-Drive-Cycle

 

Define "expensive". Here's what you need.

 

yea I should get the sticker, I have been putting it off for month and I was at the shop this week the day before the CEL but they closed at 2:30 for some reason....I am really kicking myself. Ill get the fail sticker if the fuse didn't fix it, after driving 5-10 cycles. Worst comes to worst, in 6 months I wont need to pass emissions for a sticker (car will be 15 years old). I did start it tonight after the engine cooled down and I did hear a vacuum sound for about 30 secs and then shut off. It's actually sounding better than even. I think the extreme heat this week 80s-90s caused the fuse to blow or something. I dont do a lot of highway driving too and I know short distance, slow miles are prob not the best for the engine. I did order the OEM Hella 12v relay for the pump just incase for $14 off ebay.

Does getting a ticket for no sticker increase your insurance rate? I'll keep you posted on if the code clears. I play on testing the pump too if I hear something that doesnt sound right. Thanks

 

Haha I got the $25 one off amazon. I mean how often am I going to need it, hopefully not many lol

 

I forgot to mention, when I cold started the car tonight with the hood open and cover off, I could feel a decent amount of wind and I could smell exhaust right above the pump/engine. Is the exhaust smell (no smoke) and wind normal from the belt or could there be a leak? The hoses appear to be connected and in decent shape.

 

Tim, thanks! The only problem I see is that it says the drive cycle will not work if the CEL is on.....thats the whole reason I am doing the cycle, to clear the CEL so it doesnt make sense to me. The fuse was burnt and so far thats all Ive done. Everything sounds fine now so Im hoping the CEL goes away after 10 trips.

 

I believe expired inspection sticker is considered a moving violation and goes against your insurance. Its not worth it considering theres no penalty for getting a rejection sticker.

You may feel some slight air movement in the engine bay from the belt and pulleys rotating. You shouldnt really smell exhaust, unless theres a leak in the exhaust manifold.

I have a $13 Konnwei KW310 reader and it has an I/M Readiness function so surprised yours doesn't.

Im wondering if you have more faults causing the check engine light but your reader isnt able to see them?

Try disconnecting the negative battery cable for a few minutes, see if that at least turns the check engine light off.

I rememebr someone had an issue with a faulty purge valve or something along those lines, it took them maybe a week of driving before they came back and said the check engine finally turned off.

 

this is the one I have it has I/M readiness
I just need to figure out what that means and how to use it, could you explain? Thanks

 

I have never used it before. Im guessing just click on it and it will show each monitor.

For the check engine light I think it will take a week of driving around for it to fall off, if the issue is fixed. UNLESS you follow the specific drive cycle to get it done quicker. I came across more info on the drive cycle.

 

UPDATE: just checked the 40 amp fuse for the secondary air pump and its blown, I knew I'd never get that lucky. So now I think it must be the pump itself. I am debating if I should fix try to remove and install a new pump myself. The videos make it look pretty easy but has anyone done the job them selves? I am def not a mechanic and have almost no experience working on cars. I'm sure it will be very expensive to have it fixed at the shop. I might just drive my backup 09 Camry and wait the 6 months for the car to be 15 years old in which case the CEL for emissions wont matter. The 09 Camry is a great car, I can not say enough great things about it. I can actually drive over potholes and sewer covers like its nothing compared to the C300.

 

I never worked on the pump but it looks simple to install. Can buy a new Bosch, or even look for a good condition used one on eBay.

Heres an article with photos how to replace it: https://www.pelicanparts.com/techart...eplacement.htm

 

Then you wasted $25. You will need and use it a lot more than you think. Plus the cheap $25 OBD reader is not going to scan all the modules in your car, so when the traction control light comes on, you'll not know why and end up paying the dealer $200 to diagnose your car. Is this your first Mercedes?

 

Interesting that FCP sells a "kit" that includes a new fuse and relay with the pump. That could be an indicator that a bad pump will blow the fuse and burn up the relay.

 

I was looking around for the cost of a good used pump and seems they are around $50-60. Probably best to go with a new pump though I would probably get a used one.

Looking more into why the pump would fail it seems water may be a reason, faulty wiring, or even faulty check valves. The check valves should be inspected to make sure they are functioning properly, if they are not that can cause exhaust to travel back to the pump. You mention smelling exhaust, so this is why I mention it. Ive come across threads where people have faulty, clogged/blocked check valves or even its blocked in the engine past the check valves. Wouldnt want to install a new pump and it fails again. Good news is these are easy to work on.

 

yes first Mercedes. Im starting to think I should just fix it and sell it. Seems like there is a lot of maintenance and issues when they get older. My 2009 Camry runs like a top and minimal repairs, just the basics.

 

UPDATE #2: So I got my multimeter to check the resistance on the pump terminals. According to my research, the resistance should be less than 1. Well the readings I got were all over the place and def more than 1 ranging from like 3-18. Next I hook up my alligator clips from the battery to the pump and nothing but sparks, the pump did not turn over at all - hence the 2 blown fuses. The + and - on the pump are label as a 1 for + and a 2 for -. So the pump is dead, not moving at all. Just ordered a used OEM Bosch for $55 on ebay off an 08 E350. I figured get a used bosch over a new Chinese one, I just need to get the sticker for the next 6 months until my car is 15 years old. Also purchases a OEM Hella relay for $14. Plan on replacing that as well. I'm hoping switch the pump out, a new relay an fuse will fix the CEL, we'll see. While I'm installing the new pump I am going to check both Valves and hoses to see if there is water or build up. I read that if you stick your finger in there it should come out pretty clean, if there is a lot of buildup they could be failing. I think code P0400 (which I did NOT get) stands for “Exhaust Gas Recirculation (EGR) Flow Malfunction.” It is triggered when the flow of exhaust gas recirculation is lower than what the powertrain control module (PCM) expects. So if my Bank 1 & 2 valves were failing I believe I'd be getting these codes as well. The heart of the EGR system is the EGR valve, which redirects a portion of the exhaust gas into the engine intake manifold to be integrated into the air/fuel mixture.


I plan on taking my old pump apart to see what failed, I'm guessing its a ton of carbon dust, maybe water. This past winter the remember the pump making a super loud whining noise on cold starts for ~30 secs, I'm guess that was the beginning of the end for my pump.

Some helpful videos:
shows the electrical side
shows how to remove the pump, looks pretty easy and I already have the T30 needed

 

So on the I/M readiness I got: Misfire OK, fuel system OK, Evap INC, Sec air system INC, A/C refrig N/A, Oxygen sens monitor INC, Oxygen sens htr OK, EFR System INC

 

Thats what I was thinking and its only $160 plus shiping for a new Bosch pump, relay and fuse. I opted for a used bosch off ebay for $55, relay $14 and fuse $5. I'm cheap and will see if I can save $100.

 

The "INC" im guessing means incomplete? Makes sense with the faulty secondary air pump.

I bave had good luck with my W204 but I work on it myself. If I had to bring it somewhere and pay shop prices I dont think it would be worth it. Seems there is always something to work on and replace, worn control arm, failed sway bar link, purge valve, broken coil spring, worn shocks, then theres trans service and coolant once it gets into the higher miles. Spark plugs, thats on my list. Cant forget leaking oil filter housing gaskets though that takes care of the coolant and oil change at the same time.

I prefer buying used Mercedes branded replacement parts over aftermarket.

 

Yes they mean incomplete. Also I forgot to mention, when I was diagnosing my secondary pump, there was white paint on the + terminal, I'm guess the previous owner had it replaced or work done on it at some point. So a year about I got my first CEL and it was #5 ignition coil. Luckily that was very easy to fix myself for $35 for OEM off amazon, I believe its Bosch as well. The coil is literally right on top of the engine and I took the old one out with a T30, dielectric greased the new one and popped it in, didn't change the spark plug and CEL was gone.
I also had the drivers side interior door handle break which I was able to fix, Mercedes wanted me to buy a whole new panel as it is not meant to be fix. When I fixed the handle, I learned that someone had already glue it once, so I had to replace the actual handle which included grinding some plastic rivets off and it was quite a job but saved around $1000.

Now that my 2010 C300 4Matic Sport has 88k miles on it, do you think I am going to have to start putting a lot of money into fixing it? I am having issues with the A/C not always turning on, so I have to leave it on all the time otherwise it's 50/50 whether it will blow cold air, a common problem from what I've read. When it's on and working, it works great but when its on and not working, it just blows slightly cooler air that outside temp. I also have problems with my headlights, I have to leave the settings on automatic otherwise they can stay on even after I turn them off. It drained my battery one night but leaving them on auto works as I haven't had a problem since, but I would like to be able to use my fog lights whenever I want. My point is, I don't want a high maintenance car, do you think it would be wise to sell it now? It runs great but I'm concerned about the future.

 

Mercedes are great cars, but they are not a Toyota and you cannot treat them like one. If your car has been well maintained, it should give you many miles and years of service. My 2014 C350 has a little over 127,000 miles and runs great. I do all of my own services, though I did let the dealership do the last tranny service. I provided the parts and paid the labor, which was about an hour and a half. I have done the tranny service before, but at the time didn't feel like doing it in the middle of winter.

I really can't advise you what to do since I don't know what condition your car is in or your particular circumstance, but you bought the Mercedes for a reason. You just need to decide what you want from a car.