E350 Blueefficiency Engine Management light Issue

[Adrian Jakeman]

Hi Everyone,

I have an issue with my 2011 w212 E350 whereby the engine management light comes on during a long journey especially when the car is under acceleration for example on an incline. The error code is P062F which is hard to diagnose but last night I also observed that when changing mode from E , S and M the gears will not go beyond 5 and the temperature gauage droped from the normal operating temp of around just over 90 degrees to reading 60 degrees. Now the outside temp was cold at 11pm but I had just driven the best part of 70 miles so wouldn't have expected this to have happened. The car has had a remap and there was an issue with the inlet port shutoff motor but this was coded out plus it's just had a transmission fluid service so I know this is not the issue. I was thinking of having my local merc dealers flash the software as part of the immissions issue for free just in case it's the remap but obviously that will then bring up the inlet port shutoff issue which I don't mind having redone for £50

I have run scans with WOW and Delphi with both showing similar errors so is there anything else like sensors etc I should look for or has anyone else had the same issue. The car has done 193000 miles.


Thanks,

Adrian

 

[malcolm E53 AMG]

First thing to sort out is the thermostat if the temp is dropping, mine stuck open at 65k miles and the mpg dropped to circa 20 when I should be getting better than 30mpg, the engine management system relies on data from the stat to operate properly

 

[brandwooddixon]

I suspect the thermostat.
I don't know the engine that your car has, but mine has an electronic thermostat and it did fail giving similar behaviour to yours i.e. town driving fine, but any long run on a motorway in cold or cool weather tripped the EML.
The fault that mine had stored was about the engine temperature being lower than expected.

 

[Adrian Jakeman]

First thing to sort out is the thermostat if the temp is dropping, mine stuck open at 65k miles and the mpg dropped to circa 20 when I should be getting better than 30mpg, the engine management system relies on data from the stat to operate properly

Hi Malcolm,

Please excuse my ignorance but where on the engine is the electronic themostat and when you replaced yours did the warning light go away without clearing the error code. Any photo or diagram would be helpful as I have no idea where it is located please?

Also going to run another code scan now to see if any other errors are picked up.

Thanks,

Adrian

 

[malcolm E53 AMG]

Hi Adrian,

The engine temperature gradually decreased over time on the gauge so I had a good idea the thermostat was starting to fail. The engine didn’t throw a fault but when the stat failed fully open the car started to run extremely rich obviously affecting the fuel management into thinking the car was running cold and the mpg went down to 20. I didn’t run the car much after that until I had the new thermostat fitted which solved the problem

This is the stat - a word of warning don’t be tempted to fit aftermarket they don’t work very well

https://www.ebay.co.uk/itm/Genuine-Mercedes-Benz-OM642-Engine-Cooling-Thermostat-A6422002215-NEW-/121788420290

Hope this helps!

 

[ajlsl600]

This business of complete housings to get anything is really p me off! How green is that
I wonder if there is a market for housings hade for the statts that will support a simple stat change. A number of benz models use this consumer fd system and prob other makes as well ?

 

[ajlsl600]

9euro v150 !!!

 

[Adrian Jakeman]

Hi Adrian,

The engine temperature gradually decreased over time on the gauge so I had a good idea the thermostat was starting to fail. The engine didn’t throw a fault but when the stat failed fully open the car started to run extremely rich obviously affecting the fuel management into thinking the car was running cold and the mpg went down to 20. I didn’t run the car much after that until I had the new thermostat fitted which solved the problem

This is the stat - a word of warning don’t be tempted to fit aftermarket they don’t work very well
https://www.ebay.co.uk/itm/Genuine-...ling-Thermostat-A6422002215-NEW-/121788420290
https://www.ebay.co.uk/itm/Genuine-...ling-Thermostat-A6422002215-NEW-/121788420290

Hope this helps!

Hi Malcolm,

Thanks for this but my next question is where is it located on the engine. I'm happy to change this but with my car once the fault is cleared I would think the temp would run normal again until the fault reappears. I've cleared the fault before but never noticed the temp gauage issue.

 

[Adrian Jakeman]

View attachment 63236 9euro v150 !!!

This looks nothing like the one in the ebay link on Malcolm's post so maybe you are confused or have the wrong model in mind!!!

 

[Adrian Jakeman]

I suspect the thermostat.
I don't know the engine that your car has, but mine has an electronic thermostat and it did fail giving similar behaviour to yours i.e. town driving fine, but any long run on a motorway in cold or cool weather tripped the EML.
The fault that mine had stored was about the engine temperature being lower than expected.

Your description of the fault sounds exactly like mine. Just condering if taking stat apart and cleaning can resolve the issue?

 

[malcolm E53 AMG]

There is a link to the job on uTube which for some reason won’t allow me to link but do a search for:

‘Mercedes E350 P0128 Thermostat replacement Step by Step DIY W212’

 

[Adrian Jakeman]

There is a link to the job on uTube which for some reason won’t allow me to link but do a search for:

‘Mercedes E350 P0128 Thermostat replacement Step by Step DIY W212’

Excellent thanks again Malcolm, Might just be able to get away with the stat itself minus the housing if lucky!

 

[malcolm E53 AMG]

Just a reminder Adrian better to buy the genuine MB part some have tried to replace the stat itself without success and other have bought aftermarket units which are a lot cheaper and they have been problematic. the job isn’t an easy one so the consensus is to fit genuine in this case