I wanted to provide an update to my check engine light coming on and then going off for the past 2 weeks. I posted about it in here under another members thread asking for help with why their CEL was on, but in the interest of helping someone in the future with this issue, I thought it was best to start my own thread about my specific issue. It started on Aug 21st when my CEL came on while driving for no apparent reason and no warning messages or other indications of anything wrong. The engine was running fine. The previous day, I did get all 4 TPMS sensors say out of range error even thought the tire pressures where within spec. A little low, but still within spec. That I fixed with verifying the pressures while cold and then resetting the TPMS.

I sent a text message to my service advisor asking if they can do a remote diagnostic (it was after 6pm) and to my surprise he responded within a few minutes saying they would do so first thing in the morning. The next morning, my advisor told me that they believe a software is needed and I would have to bring it in. The first day for a loaner was September 1st and so I made an appointment. I had another USB media issue to have them look at and I wanted to get the E333.8-58 update as well so I had a list of things for them to check out besides the CEL. Today, I was told that the CEL is coming on due to a faulty exhaust flap that isn't closing. Fault code P140473 "exhaust flag 3 has a malfunction". This flap is used to reduce exhaust noise and doesn't aid in performance or any other function. Doing a little research, I found that for gas engines it's strictly an acoustic thing and not needed from a functional standpoint. In any case, my service advisor told me that this has been a common issue with the W214 E450 specifically (not E350) and that MB is saying the exhaust has to be replaced. The problem is, the part in question is being redesigned and isn't currently available. I'm told that it will likely become available within the next few weeks but they are not certain on that timeline. Until then, I will have to live with the CEL being on sometimes (it goes off some times) until they get a replacement. The CEL only goes on when the flap sticks open. It came on not long after leaving the dealership. I'm about to take a long 1,600 mile round trip to FL next week and my service advisor said there is no issue driving the car like this. I'll just have to learn to ignore the CEL when it's on.

I'll update this thread when things change. Hopefully this helps others who might be facing this issue and be an example that if you have a CEL on, don't ignore it. Have it checked out even if the car is running fine. By the way, the USB drive issue was resolved with the software update to E333.8-58, but I'll discuss that in another thread. I want to keep this one focused on the CEL and the exhaust flap fault.

 

The CEL can certainly be ignored in this case, based on what you described (no real wolf at the door).

But what if a real CE situation presents itself (for whatever reason), and you drive around thinking it is the existing flap-related situation, and ignore it ? I would thus be cautious and wait till it gets properly fixed, and keep an eagle eye out for anything unusual, in the meantime.

 

How much of the exhaust has to be replaced? I wonder if the E53 CEL coming on is the same issue?

 

I'm not sure. I'll know more when it time to have it replaced. It's possible since they have the same engine.

 

If the CEL is on AND the exhaust note is loud, indicating that the valve is stuck open, then the CEL light can probably be ignored. It's not clear whether or not the valve must be stuck in a completely open position, or just partially open, to trigger the CEL.

Presumably, the CEL comes on after the car has been running in Sport/Sport+ mode, the driving mode is changed to Comfort, and the exhaust valve remains open. I wonder if the CEL light will turn off due to this error condition if the mode is changed to Sport/Sport+?

 

My car is in for service since yesterday and one of the things I asked them to look into is the CEL coming on. I saw this posting before dropping the car off, so very interested in finding out what they identify as the reason. My service advisor previously told me that if the CEL is on not to worry about it unless it is blinking. If it is just on, typically just a sensing something not working correctly, and you can drive the car until you bring it in to have the issue resolved. If it is blinking that could be a more serious issue.

 

To add to the above, another scenario:
CEL is on AND the exhaust note is loud AND a different unknown situation on top of this, also contributing to the CEL => CEL to be constantly eyed till situation is fully rectified.

 

This is really helpful info for me, I've been dealing with the same issue the for the past couple of months.

 

An update to my issue described above. The CEL has now been on for over a week straight where as before it would be on for a day or two and then off for a day or two. The parts (below) are on order and if you search for them it will show as discontinued. I suspect that could be because MB has redesigned the part (according to the service advisor), but I'm not really sure. The MSRP for all three parts is just over $1500 but this is being covered under warranty as it should be.

214-490-15-03 - Exhaust System (left)
000-995-24-04 - Pipe Clamp
000-995-21-04 - Pipe Clamp

I have an appointment at the end of the month to have this work done. Until then, I'll have to live with the CEL on all the time now.

 

Hopefully, this is a well engineered solution, and should fix it once and for all.

 

I doubt if the parts are designated as Discontinued because they are being redesigned. Many W214 parts are categorized as Discontinued. Frequently, when you search for W214 parts the results list W213 parts claimed to be compatible with the W214 chassis. I have two theories for the reason that so many parts are listed as Discontinued. 1) The parts are in short supply and are reserved for new production. 2) The people responsible for maintaining the online parts catalog are totally incompetent. More and more I am thinking it's the latter.

 

Or 3) The current supply is sufficient and no additional production is planned.

 

My CEL just turned off today after being on for two weeks, I started tracking it and I do see a pattern that it turns on and off based on weather and temperature, it turns off when it's cooler and on when it's hot.

 

Have you gotten it checked out to find out why?

 

The parts came in on Monday and I had the car in for service today. Basically they replaced the left muffler and flap. CEL had been on constantly for over 2 weeks and is out now.

If you have a CEL on. Don't ignore it.

 

I have another appointment next week. I took it in back in mid Aug when it first came on, all they said were it was only a software update, then the light came back on and off the subsequent weeks.

 

Do you have an E450? If so, it may be the exhaust flap like it was with mine. One of the things I noticed on mine was that when the car was running I could feel exhaust coming out of the right muffler but not the left. The left side is what was replaced on mine. I was under the impression that it was stuck open not closed which would seem odd that I didn't feel exhaust coming out of the left with that being the case. If it was closed, I would expect to not feel exhaust. In any case, it's fixed.

 

Out of curiosity, wondering if the folks who got the CEL, drove in Sport mode ? For reference, I drive almost exclusively in Comfort mode, or in the Individual mode, where my Individual settings have the Engine set to "Comfort" and everything else to Sport.

 

I would say 99% of the time I'm in comfort mode. I will occasionally put it in sport mode for brief periods of 2-3 minutes if I want to drive spirited, but then back into comfort mode. I've tried eco just a couple of times to try it. I also take it easy on the engine when the oil is not fully up to temp and will drive easy for the last 5 minutes minimum before parking. It's a luxury sedan and I try to remind myself of that but the E450 will get up and go if you ask it to. It's no E53, but it's no slouch either.

 

I do have E450 and I do Sport mode almost 100% of the time

 

Have you brought it to the dealership to diagnose the CEL being on? Very possible it's the same issue as mine. Regardless, you should find out and post back so we all benefit from that knowledge.

 

In the X213 (2022 E450 All-Terrain Wagon), which had the exact same Inline-6 Turbo with the 48V mild-hybrid system, they used to have "Sport" and additionally, "Sport+". Interestingly, in the "I*" (Individual) settings, they would not allow the engine and the suspension to be set to Sport+. The Sport+ stood separately on its own. And even when one was in Sport, when you switched to Sport+, you could immediately sense the Suspension tightening down, and the engine going into a totally different level. The X213 also had a dual-chambered Airmatic, unlike the single-chambered Airmatic of the 2024+ models.

For whatever reason, when it came to the X214 (my current 2025 E450 AT Wagon), they eliminated the Sport+ from the E450 (while retaining it in the E53). And even the Sport in the X214, seemed to be a bit of a watered down setup, and thus I never even bothered to switch to "Sport", other than the "I*" setting where everything is set to Sport, except the Engine, which is set to comfort. To me, when it came to the X214 E450, "Comfort" seemed to be the design theme, and I am perfectly fine with that.

Coming back to the theme of this thread, I have a suspicion, that the CEL is connected to the Engine's "Sport" setting. That the flap within the Exhaust behaves differently, when set to "Sport", and when the flap gets stuck for whatever reason, it triggers the CEL. To be verified by MB, via a detailed engineering analysis, of course.

 

Not in my case. I rarely use sport mode and the CEL was on regardless of mode. Maybe the flap fails while in sport mode and is then permanently failing thereafter, but that's hard to say. I doubt it with as much as I drive in comfort mode and I typically baby the car. I'll get on it once in a while like if I need to enter a fast moving highway, but that's about it.

 

In my case, the car is almost always in "Comfort" or in "Individual". The Individual settings are set to "Sport" in all parameters, except for the Engine, which is set to "Comfort". I set the engine to "Comfort" in the Individual settings, because the engine revs higher, when set to Sport.

I do redline my car at least once or twice a week (after she's fully warmed up over 10-15 miles) but the base setting is "comfort". Of course the flooring/redlining only lasts for a few seconds, since by then the car is already hitting triple digits, and don't want to be pulled over.

My finding is that once you floor it, the car goes "all out", without being in the "sport" setting, and disregarding any drive-mode setting. I also suspect, that the exhaust situation comes on, only when the "Sport" drive-mode is explicitly chosen, and not when the car is floored and redlined. This is all speculation of course.

 

I always assumed the flap was just for quicker warmups and opens once the temp is up. On cold start, I only have exhaust from the right side.