Missing mpg on instrument panel

[JayDeeCee]

HI All
I have a 64 plate C220CDI AMG Line Coupe , 43,000 miles, serviced regularly, which I got from MB Dealer 2 to 3 years ago.
Generally speaking apart from a split EGR cooler, a leaking fuel pipe into the filter, and oddly having to replace the discs all round after only 29,000 miles I havent had any major issues. but I have a question concerning the long term mpg calculation displayed on the computer.
I had the MB update performed last year and didnt notice anything until this winter. I noted that the mpg had dropped noticeably, from arounf 60 on a motorway run to around 50 and much more severely on local driving. I note that this seems to be a common isuue on the threads.
I hadn't checked the long range mpg calc for some time, so decided to check it on the computer and its is not showing a value, just 3 dashes. It shows the miles since last reset 24,800 and the total up time 915 hrs, but not the mpg.
Anyone got any ideas as to what is causing this?
Cheers

 

[Nicklas_Hidegard]

After I had the update on a previous car (v220d euro6) the long term trip was automatically re-set. Might be that the difference in calculations (guessing here) don't allow for mpg calculations using before and after values at the same time. Try resetting it and it should work ok.

Sent from my VOG-L09 using Tapatalk

 

[JayDeeCee]

After I had the update on a previous car (v220d euro6) the long term trip was automatically re-set. Might be that the difference in calculations (guessing here) don't allow for mpg calculations using before and after values at the same time. Try resetting it and it should work ok.

Sent from my VOG-L09 using Tapatalk

Thanks, its odd as it was displaying after the update, but at some point decided to stop displaying. I reset it but it still didnt work, so I reset it, shut it down left it and reset it again, and it seems to be displaying again now..

 

[Botus]

maybe you have a fault and its also impacting the mpg...

"I had an MB update" there is no such thing - there are multiple modules on the car and they mostly not connected in terms of how software updating is performed. The only usual multi-update as one defined process is only for the in car entertainment. Everything else is a one by one muddled mess

There have been a number of "issues" found inside Merc engine ECU software. With the USA EPA and the EU searching for "interesting features" in emission control systems on motor cars certain "extras" you may not want on your car have been "discovered" and manufacturers were asked to bring the cars back and fix them.

We should perhaps get a little more excited when we see this sort of thing

Daimler AG (“DAG”), the manufacturer of Mercedes-Benz vehicles, has determined that on certain Model
Year (“MY”) 2012-2014 Mercedes-Benz vehicles of various models (117, 166, 172, 204, 207, 212, 216,
218, 221, 222, 231, 251, and 463 platforms) the software of the Engine Electronics Control Unit (“ECU”)
may not meet production specifications, which could result in a Malfunction Indicator Light being
displayed while no fault is present in the control unit. An authorized Mercedes-Benz dealer will update
the engine ECU software for the affected vehicles.


Daimler AG (“DAG”), the manufacturer of Mercedes-Benz vehicles, has determined that on the various Model Year (“MY”) 2014 -
2018 Mercedes-Benz vehicles listed below, the engine control unit (ECU) software may not meet current specifications. In certain
circumstances when the vehicles are parked for a long duration, an erroneous activation of the “Check Engine Lamp” from the
outside temperature sensor might occur.


I wrote this as an indicator of the "fun you get with Mercedes' software updating method" just last week...

It would be great if we had insight in to what software changes were for and knowing what to apply to give all matching, compatible software. But there are legal / safety reasons they don't disclose the why to anyone.

It appears Mercedes "thinking" was everything is comfortable and doesn't need to rely on the software iteration in other modules on the car - but that is NOT the case. It seems true that much operates successfully, but some do need another module updated, or once one is updated another might now accept an update that was not visible (without doing other modules first). And then if that too is updated we discover (if we look) a critical update for another is now compatible. Its rather a mess, and they need to start again with how they make cars.

Very occasionally the dealer tools will alert the operator to the need to do another module. But I've seen it forget to do that during this session. Then when next plugged in it offers the change. And I've then see it make errors when you do that and break things, and then years later (I guess after other customer complaints) they realise oops, we never turned that on or configured this part correctly !!! Rather serious omissions, that should never happen.

BMW is the ONLY brand I know of that does things the best way - flash everything in the car during the same session, going around all modules in the car one at a time, in a set order, pushing all latest fixes and for belt and braces over write any module that isn't getting new software with a fresh copy of its current standard, then as each module finishes its individual programming, re-confgure everything in that module to its factory set up. If it dies you know the offending module or the next one in the loop that shouldn't be there as its not factory approved fitment.

Had this done on 1 car and 3 bikes (only the car played up as I had fitted the CD multichanger in the MOST loop and BMW though having pre wired the car for the module, wasn't aware it was now on the loop - so was trying to flash BT software to the CD changer - when I pointed this out they added the cd changer to a list of toys on the car (equiv of updating the Datacard) and the car updated without issue. It went much much faster (twin turbo nutter car), did better MPG, the gearbox worked better, and the interior toys got an update, allegedly updated the car to suite current dealer diagnostic tools and added current dealer info for all europe BM garages. And cost just £121 to do it on the car - On one of my bikes its only a 20min labour charge