Hello,

I have a stock 2014 E63s with about 60K miles on the clock. I've had random but continuing issues where the car dies at a stop. I have SDConnect with Xentry, and have pulled codes several times. The only thing the pops up is a B1F8D14, "The lower sensor of the rear switching module has a malfunction. There is a short circuit to ground or an open
circuit."

In an attempt to isolate, via Vediamo, the ECO Stop/Start function was permanently shut off because it first seemed as if the dying only happened when in ECO mode. Problem still exists. I know there is a "Relay Starter-Alternator Backup Battery" (A0009822023) that may be involved. A Google search of the code points to this site: Autologic Live: Electrical fault malfunction on Mercedes C-Class - autotechnician - servicing the independent workshop. Not sure it relates.

Any ideas of what might be causing this? Also anyone know what the "lower sensor of the rear switching module" is? Seems odd that the car doesn't throw a code when the car dies unexpectedly.

Thanks,

Joe

 

Sorry to go off topic . But the eco stop/start can be permanently turned off ? through star etc i'm assuming
.Just saw the Vediamo note - got it

 

Correct, and it's quite a process that was done for me by BenzNinza, while I watched, LOL.

 

First, thanks for responding. Help me understand a "very good scan". Is there something better than Star, or are you referring to a scan related directly to the rail pressure?

 

Hello Joe, you may want to look into the sensor system for the trunk lid opening/closing. The 2 sensors are essentially wires that connect to the switching module. The attached WIS article AR80.61-P-0012EW may be of assistance to you. It calls for the rear bumper removal, but you may be able to get away without it. Hope this helps.

 

Thanks for your response! What leads you in that direction? Don't mind bumper removal, but would like to understand the need first.

Regards,

Joe

 

I searched WIS for key words from the error code you posted. The only hit was the article I uploaded.

 

Never mind. Finally got it.

Thanks!

 

Here are the part numbers and reference costs.

[640] A2124405058 Electrical Wiring Harness $17
[660] A2059052110 Rear Switching Module $95
[680] A2229059004 Sensor Top Coding A $35
[690] A2229058804 Sensor Bottom Coding B $37
[695] A0295451026 Coupling Housing Coding A 2-Pin MLK1.2 $5
[695] A0295451126 Coupling Housing Coding B 2-Pin MLK1.2 $5


212.076 Rear Bumper

 

@Valvestud With a nearly 8 year old vehicle, what is your opinion on changing the battery? And if your vehicle at one time had start/stop, it also has either a capacitor or auxiliary battery. What do you think about replacing the capacitor or aux battery?

 

Thank for the reply. Both batteries are new. Not sure what "capacitor" you're referring to. Can you elaborate?

 

I think it's the C-Class that uses a capacitor, rather than an auxilliary battery, for the eco start/stop function. If you have replaced both batteries in your vehicle, that box is checked. The search function will bring up references to the capacitor.

 

There is a "battery backup relay" that might be related to the issue. Was hoping to get more user experience data before going down the road of replacing parts one at a time.

Also may be fuel related as suggested by another member.

Thanks!

 

This can be accomplished very quickly and easily with our OBD programmer.
You can program your vehicle to remember what the last eco start/stop setting you have it on (On or Off).
Check coverages HERE

 

So during a session on Xentry today with Peter (BenzNinja), we did a deep dive into the error related to the ECo Start/Stop fault that relates to the bumper sensor. The faults relates to the up/down sensors not responding accurately. Still doesn't seem likely this is killing the car, but I will investigate anyway to fix.

Thanks again!