dpf exhaust sensor replaced - another or related issue?

[Deleted member 160853]

Hi Guys!

Had an issue with my dpf exhaust pressure sensor giving incorrect readings so had that replaced and a force regen done however something else keeps happening.

Sometimes when I switch the car off & back on if I pop out or have been on a long journey and come to a stand still then start driving again something triggers the car to start hold gears for a reason unknown to me, it's driving me mad

I'll be driving in e mode and it holds gears to around 3k RPM and when I put my foot down its super un-responsive, attached a video if that helps at all, you'll see it holding gear one till 3k revs.

Streamable Video

Could this be the gearbox or still DPF related?

 

[Deleted member 160853]

As mentioned its not happening all the time and no engine light appears, the dpf has been regen'd so I'm running out of ideas..

When it's driving normally the gearbox is smooth etc, has recently been serviced too.

 

[Deleted member 160853]

bump

 

[Deleted member 160853]

bump

 

[bartebk]

Sounds like limp mode?

 

[Deleted member 160853]

@bartebk yeah I think so too but I'm not sure what triggers it, it drives fine half the time, no engine light etc, was wondering if anyone had a similar issue.

 

[bartebk]

I’ve been having DPF problems since last year, initially warning light, DPF soot content, then into limp mode. Manually removed DPF’s, cleaned them out, refitted, then had DPF reset, problem solved I thought.

1 month later, approx 700 miles, same again, I can’t believe the DPF’s are full again, especially given the fact I’ve done approx 300 motorway miles.

I’m thinking a sensor, as it can’t be a ‘mechanical’ issue

 

[Deleted member 160853]

Yeah at this point I've had it force regen'd twice in the past 3-4 months so I'm leaning on the side of a sensor issue.

I guess its trial and error to find out which one since no engine codes are appearing at the moment since the new sensor and regen as of yesterday and the issue has come back.

Also I'm pretty much only doing motorway journeys too.

Looking at some past threads maybe a boost pressure sensor/clogged EGR valve.

 

[bartebk]

if I get anymore information on my problem I’ll let you know.

I did read an article about the Mercedes software update that was applied to mine at the last service, October 2021, my problems started approximately 6-8 weeks after this, coincidental?

 

[Deleted member 160853]

Hmm potentially.

Will you be having it checked again?

I'll keep you posted on mine, heading back to the indy on Monday!

 

[bartebk]

I’m going to contact them, want to eliminate all possibilities as what is causing the problem. I did also read in the same article that if you have any problems after the software to do with sensors in exhaust system Mercedes are covering these for 24 months after software update

Don’t know if this is true or not, I’ll find out when I call

I wish the Diesel engines were the way they used to be, seem a lot more problematical now

 

[MilesWFB]

Just wondering if on the OP's car it can alter shift ranges?

On mine, if you pull one of the paddles when not in 'M' mode (gearbox) a number will appear next to the 'D' on the display and it will stay in gears for longer, used for engine braking I think.

I don't know if this is a thing on newer Mercedes. sorry if I'm wrong. only a thought.

 

[W1ghty]

The car will have logged fault codes which the Indy will see on Star diagnostics

 

[OneForTheRoad]

If a new dpf sensor is fitted ,it must be adapted to the car , otherwise pre stored data is used , the car won't know its a new sensor . Hence its still seeing 300% fill levels. As mentioned above , all error codes must be erased to stand any chance of even getting a dpf regen , any stored codes and the car just won't play .

Live data for the exhaust back pressure sensor is also very helpful.

 

[jc651]

My car was doing the same thing and when I did a code read it come up with a historic fault codes for the exhaust back pressure sensor. After clearing the code it was fine for a few weeks and then it done the same again so it cleared the code again and this happened 4 times before I changed the sensor and it's been fine for over a year now. Not sure why it affects the gearbox holding onto the gears but it's a sure sign that the sensor is playing up and it's a easy job to change yourself. The sensor was £57 from my local MB dealer and they keep a good stock of them because they often fail.

 

[OneForTheRoad]

My car was doing the same thing and when I did a code read it come up with a historic fault codes for the exhaust back pressure sensor. After clearing the code it was fine for a few weeks and then it done the same again so it cleared the code again and this happened 4 times before I changed the sensor and it's been fine for over a year now. Not sure why it affects the gearbox holding onto the gears but it's a sure sign that the sensor is playing up and it's a easy job to change yourself. The sensor was £57 from my local MB dealer and they keep a good stock of them because they often fail.

The engine goes into limp home mode , meaning no turbo boost and the simplest of gear changes . To do just that , limp you back home.

 

[Deleted member 160853]

Thanks for all the input and sharing your own stories, appreciated!

@jc651 the exhaust sensor was just replaced on Friday so not sure if something else is causing it now.

@OneForTheRoad i presume they recalibrated the new sensor when it was changed over but I’ll find out Monday!

 

[OneForTheRoad]

Thanks for all the input and sharing your own stories, appreciated!

@jc651 the exhaust sensor was just replaced on Friday so not sure if something else is causing it now.

@OneForTheRoad i presume they recalibrated the new sensor when it was changed over but I’ll find out Monday!

Values should be around - 0.04 to + 0.04 for the dpf sensor . Live data

 

[bartebk]

If a new dpf sensor is fitted ,it must be adapted to the car , otherwise pre stored data is used , the car won't know its a new sensor . Hence its still seeing 300% fill levels. As mentioned above , all error codes must be erased to stand any chance of even getting a dpf regen , any stored codes and the car just won't play .

Live data for the exhaust back pressure sensor is also very helpful.

Now that could explain my predicament, thats what I’m thinking now. If I had a duff sensor causing it to go into limp mode because ?dpf full, dpf’s were cleaned and it was reset as if a new dpf was fitted and codes erased. Lasted 1 month and back to the same, got to be a sensor?

What should I be looking at via live data?
I can’t do this on Icarsoft but I’ll get it plugged in next week

 

[OneForTheRoad]

Now that could explain my predicament, thats what I’m thinking now. If I had a duff sensor causing it to go into limp mode because ?dpf full, dpf’s were cleaned and it was reset as if a new dpf was fitted and codes erased. Lasted 1 month and back to the same, got to be a sensor?

What should I be looking at via live data?
I can’t do this on Icarsoft but I’ll get it plugged in next week

Values are above.