kingoo

Hello

I have an issue with my 2016 C300, I get the error message (Start Engine See Operator’s Manual)

I took the car to an independent Service Center and they tried installing 2 new batteries (Genuine MB Batteries) but keep on getting the same error message.

And when I check (Vehicle Data) I see no (IB) reading as per the attached photo

Also, my eco start-stop function does not work at all, it does nothing when I press the button and nothing appears on the dashboard when the engine is off the button’s green light goes on and off when I press the button.

sometimes the KEYLESS-Start doesn’t work it says Key’s Not Detected, I tried changing the Key’s battery twice with no luck…

I also swapped the -ve battery terminal sensor with no changes

any ideas or fixes?
thanks a lot in advance

MBenzOwner

did you check for any xentry codes? Maybe battery sensor or something with alternator? Was IB working when you had this error
message before the battery change?

They recommend unplugging the
battery sensor when changing the battery to prevent damage.

Do you have any issues besides eco start / stop. That is rightly off because the computers sees something wrong with the electrical system and it will not allow eco start stop to work. Once the underlying problem is fixed, eco start stop may work.

kingoo

Thank You for the quick response…
they said there were no codes
also I forgot to mention that sometimes the KEYLESS-Start doesn’t work it says Key’s Not Detected, I tried changing the Key’s battery twice with no luck…
I also swapped the -ve battery terminal sensor with no changes

MBenzOwner

There’s has to be a code if you have a dashboard error message. You need enhanced Mercedes diagnostic OBD or someone with xentry software. The front SAM controls those two systems so you may need xentry access to investigate that too.

kingoo

Will try to check with xentry diagnostics
thank you

kingoo

Any Assistance would be much appreciated

Cosworth2000

Your auxiliary battery maybe faulty

kingoo

I tried to remove the aux battery and got (aux batt malfunction) error code
the code went off after reconnecting it...
so it's fine I suppose

stockbmw

You get the IB no reading when battery sensor grey clip is unclipped or is defective.

Cosworth2000

Nice.. that is good news

kingoo

which Sensor? on the -ve or +ve terminal?

stockbmw

Battery voltage sensor grey clip is right on the neg terminal.

kingoo

Thanks a lot

kingoo

After a tedious search on the internet, I found this document that helped me fix the issue

https://static.nhtsa.gov/odi/tsbs/20...34790-9999.pdf

While I was checking the wires and connector of the -ve Terminal sensor I found a disconnected red cable laying around (My guess the previous owner disconnected it to permanently disable eco start stop) and as per the above document it should be connected to the +ve terminal
I did connect it as advised and voila issue resolved and the error message has disappeared

Now I get (IB) readings and the Eco Start Stop button lights up with the engine running

the only issue now is that the Eco Start Stop symbol doesn’t show on the dashboard nor the engine shuts off

bellow are few pictures to show the fix







Thanks @MBenzOwner @Cosworth2000 and @stockbmw for the inputs

duchbk123

Good UB and IB numbers, quite similar to my car

Mikedami

Should the IB number be below 5 A once the battery is fully charged? My UB is at 14.7 and IB 2.

jjkh58

Hi - I have the same question as Mikedemi - What is ideal reading of IB should be at both idling and driving? My UB is stable at 14.3 when idling/ driving and IB goes from negative to plus when I start the engine. However, the IB gradually drops and stays around the 3~6 no matter whether the car is idling or driving.

I have seen so many articles about UB but not many around what IB should be? I guess if it goes negative while driving then for sure its a problem but if it stays within the plus range. What is ideal for IB? and why its dropping when the engine is on while the UB is stable?