Hi all,

my vehicle is a E250 2011 E Class Coupe. I've had this car for 9 years and its been great; however I've currently got an have an electrical issue...
Back story so far:

- Aux and Main battery replaced
- Aux Relay module replaced

These have not resolved the matter.
On first start up, for around 10 seconds the car is fine. Both batteries read 15.1V. So I believe that the alternator is fine and everything is as expected. however after 10 seconds the battery light pops up and the charge to the main battery does not work anymore and is a constant 12.4V. I've driven the car like this for a while now and the alternator still works to power the vehicle as I'm still able to do long commutes with no issues etc. the aux battery and relay module still all read 15.1V after this fault code.
At this current time it also has a voltage drain (I suspect this is what is scrambling the signals). I currently hacve to charge my main battery once every two weeks.
Faut codes I have:

- B221D49 - The rain sensor has a malfunction. There is an internal Electrical Fault
- B221D54 - The rain sensor has a malfunction. Calibration is missing
- B2299-49 - Control unit rear passenger compartmenet has a malfunction. There is an electrical fault
B21DF-71 - The relay of starter battery has a malfunction. The actuator is blocked
U1169-00 - Communication with interior pretection sensor 1 has a malfunction. there is a general failiure
B25A6-64 - Door contact driver door has a malfunction. there is an implausible signal
B210C-16 - The power supply is outside the valid range. The limit value for electrical voltage has not been attained
B2191-16 - The power supply of circuit 30g is outside the valid range. The limit value for electrical voltage has not been attained.
540410 - The result of the voltage measurment in control unit A76 (Left front reversible emergency tensioning retractor differs from the result in control unit N10/2 rear passenger compartment SAM Control unit with fuse and relay module
510116 - The supply voltage of control unit A76 left front reversible emergency tensioning retractor is too low under voltage
640300 - Software error
B23A8-13 - The output for the window heating has a malfunction. There is an open circuit
B210C-17 - The power supply is outside the valid range. The value for the electrical unit was exceeded
U1160-00 - A bus keep awake unit was detected. there is a general failiure

So as you can see a load of faults. I believe whats happening the drain is of part of the issue here its scrambling the signal and perhaps its on the auxilary line, causing the issue?
I really dont have a exact clue, I'm just guessing at this point, but I'm hopingsomeone may know a small part of the bigger picture that can help me resolve this issue

Thanks

 

moved to C207 forum...

 

I have read your report. What's causing poor voltage control is not directly obvious despite a generous fault collection.
You should really stop driving this car until safely repaired.

Note 15.1 is an elevated voltage that may shorten the life of all on-board electronics.
12.5V is actually the voltage of a charged battery without further ALT power.
That means you're driving by draining your batteries.... not real stable nor safe (see belt tensioners faults).

Based on your above inputs you're likely dealing with poor ECU GND reference as evidenced by elevated voltage.

Note each failt needs to reference a status: active or stored??