Jordan Frampton

Hello all,

After rectifying my ESP/ABS fault I now have another gremlin!

Picked the car up from the Indy on Monday 5th, drove the car for a week with no issues until Sunday 11th. I filled the car up with diesel and upon restarting the engine I had engine management light come on and remained on after several restarts. I have taken the car to the Indy this morning and had it plugged into STAR again.. BUT! the fault code reads "internal combustion engine - unknown fault", there is a code that proceeds this but can not remember for the life of me, only that it started with a "D". Reset code but it will not clear and engine management light comes back after two restarts

The car is driving absolutely fine and I have noticed no difference in the running of the vehicle, low speed or motorway speed. The Indy garage are looking into this and reaching out to the wider network, but in the meantime I'm curious if anybody else has ever witnessed this?

A rough timeline is as follows... car has been in garage for 1 month with ESP/ABS fault -> repaired and driven for 1 week -> filled up with diesel (AS*A fuel) -> restart engine and now engine management light -> unknown fault code on the STAR diagnostics

The car is booked into Mercedes for the airbag recall on the steering column so maybe this will shed some more light on the issue, but I'm hoping against all hope someone has witnessed something similar before!

Thank you for any help in advance!

PaulE550

So the car runs great for a week and then you go to fill up with some fresh diesel. Immediately after the fill-up, you start the car and get the fault code. Car still runs, but the engine management system immediately detects a problem. Just not one severe enough to prevent the car from running altogether. Did anyone think to check the diesel in your tank? Perhaps you got a bad patch of diesel or there was some contamination, like water seepage into the fuel tanks at the station where you filled up, that diluted the fuel just enough for the engine management system to detect a problem. Just a thought. It seems awfully coincidental that your latest problem occurred immediately after a fill-up.

Jordan Frampton

Nail on the head there Paul - my instant thought was dodgy fuel to be perfectly honest, however the light came on straight after filling up/maybe a few yards after pulling off the station forecourt, would it not take a slightly longer time for the "new" fuel to be sucked through the pipes/injectors? after all, the tank was reading between a quarter and half tank. In any case, would this cause an unknown fault or does the fuel system have enough sensors that would pick this up and throw an actual readable fault code?

Thank you for your thoughts though, I think it is definitely something to consider. I am just slightly dubious to go on long runs in case the car throws itself into limp mode 100 miles away from home!

Harold1898

Take it to a MB dealer they will check and diagnose very quickly. If fuel why would it continue to run perfectly?