Gearbox in limp mode and yellow warning light - E350d

[ROBERINO]

Hi all. I've joined here because I wasn't getting any joy on this issue from Google.

I have a 2020 E350d that is regularly having a gearbox issue that I am sure isn't related to the gears. The car will start normally but then after a few minutes of driving holds gears up to 3000 rpm before changing up, even in low-stress driving. It does this in every gearbox mode from Eco to Sport+. I also cannot override the gear selection with the paddle shifters. This is sometimes but not always accompanied by the yellow engine warning light. If I shut down the vehicle then restart it goes back to normal and 50% of the time stays that way. The problem has been becoming more frequent over time. The DPF light isn't on.

The Merc service centre has updated the gearbox firmware/software but this made no difference. I read somewhere that this may be an emissions issue but can't find more detail than that. TIA if anyone has info on this!

 

[Larkone]

If there is an EML then there is a code and the code should start to give some indication of the problem. Surely at that age it is still under MB warranty.

 

[whitenemesis]

Classic symptoms of a failing electrical conductor plate in the gearbox (certainly in previous 'boxes) but as has been stated above the car is still under manufacturer's warranty, so get the dealer to sort it. There will be error codes. Are you taking it to a main dealer?

 

[ROBERINO]

Thanks for the rapid responses! There's a chance I'm using the term "limp mode" wrong here. I don't see any error code (where would that be shown though?). It is under warranty and I'm using a Merc authorised service centre, but I'm just a bit peturbed that they didn't identify/fix the issue the first time I took it in.

 

[Larkone]

The codes are found by using a code reader or MB Star system. The EML is just a way of telling there is a code to read, it is not displayed anywhere in the car. Time to get robust with your MB Service Centre or find a different one

 

[Notamech]

What you are experiencing seems to be "limp mode" i.e due to an error somewhere the ECU decides to limit the performance of the car which means it doesn't shift as it would normally. So it may not necessarily be a gearbox fault. As others have said once the garage runs a diagnostic using their scan tool it should tell them whats wrong. Once that has been fixed the grears should shift normally on their own.

 

[BigJase88]

Keep taking it back until it's fixed

 

[zipdip]

Well to get the best service from the dealer make sure you take the car in with the fault running,these gearboxes sometimes do not throw a fault code,so if the service is in the car when it is running poorly he will then know it is maybe the electro plate,and I suppose if it is a main dealer they will remove and replace with a new one and code it to the car.

 

[Wilfrid]

Hi all. I've joined here because I wasn't getting any joy on this issue from Google.

I have a 2020 E350d that is regularly having a gearbox issue that I am sure isn't related to the gears. The car will start normally but then after a few minutes of driving holds gears up to 3000 rpm before changing up, even in low-stress driving. It does this in every gearbox mode from Eco to Sport+. I also cannot override the gear selection with the paddle shifters. This is sometimes but not always accompanied by the yellow engine warning light. If I shut down the vehicle then restart it goes back to normal and 50% of the time stays that way. The problem has been becoming more frequent over time. The DPF light isn't on.

The Merc service centre has updated the gearbox firmware/software but this made no difference. I read somewhere that this may be an emissions issue but can't find more detail than that. TIA if anyone has info on this

The problem I suspect might be that the exhaust filter Is full which reduces
engine power. This can be an emmision issue as you suspect. If it is then check out with garage. You can damage the engine if you continue to drive. This has recently happened to me.
Had to buy a new filter. The car is now back to normal.

 

[davymead]

Unless I’m missing something, if the car is under manufacturers warranty you leave the car with them until it’s fixed.

 

[ROBERINO]

I went back as there was a yellow engine warning light this time. The diagnostics said it was a faulty power system (I forget the acronym - something like ACHV but nothing to do with air conditioning) and they reckon that once that's fixed the gearbox will resolve itself.

 

[ROBERINO]

The problem I suspect might be that the exhaust filter Is full which reduces
engine power. This can be an emmision issue as you suspect. If it is then check out with garage. You can damage the engine if you continue to drive. This has recently happened to me.
Had to buy a new filter. The car is now back to normal.

I thought that but there's no DPF warning light and nothing came up on the diagnostic test.

 

[Notamech]

I had this happen to me a while ago, in my case it was a cracked turbo boost pipe. Its a fairly common problem on mercedes diesels because the oil in the intake system degrades the rubber pipes. Might be worth checking. Also my understanding is that a solid yellow check engine light is indeed an emissions issue but that can be caused by anything from a bad turbo to a choked up egr valve. Hard to say unless its diagnosed.

 

[Larkone]

@Notamech the yellow light means there is a code for a fault - not just on the emissions side

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