CarMon225

Hello and greetings to all, my whole write up disappeared. I have edited this and retyped the whole post again:

Hello. My brother-in-law has a 2015 GLA 200 4Matic with about 70,000mi. I am fairly handy but we are brand new to Mercedes-Benz vehicles.
About 2 months ago it indicated "Auxiliary Battery Malfunction", and I ordered a generic battery of the same size and replaced it (under the dash). That solved that problem.

A few weeks later the dash began indicating "4Matic Currently Unavailable" & "Parking Brake See Operator's Manual". It would come on at times and go off at times.
Recently he was driving highway speeds (70-75mph) and those messages illuminated and he pulled over and shut off the vehicle for a half hour. He noticed while pulling over the steering got stiff also. After the 30 minutes he started up again and pulled back onto the highway. The messages were still indicating and the steering was still stiff. After some time the messages disappeared. This seems to be an intermittent problem.

I took a look at his vehicle.
I load-tested the battery: It passed.
I started the car and load-tested the electrical system again: The alternator seems to pass as under load it maintained 12v.
I did notice that while idling (no load test) the voltage at the battery was at 14.6 which seems high to me, but perhaps that is normal for this model.

I then tested the parking brakes: They both appeared to actuate when commanded, and deactuate when commanded.

I then pulled OBDII codes. 2 codes displayed (which I was not able to erase):
C003A
U140C

C003A code possible causes
Faulty Right Rear Wheel Speed Sensor
Right Rear Wheel Speed Sensor harness is open or shorted
Right Rear Wheel Speed Sensor circuit poor electrical connection

U140C Code - Implausible Right Rear Wheel Speed Signal Received
Faulty Right Rear Wheel Speed Sensor
Right Rear Wheel Speed Sensor harness is open or shorted
Right Rear Wheel Speed Sensor circuit poor electrical connection
Faulty Anti-Lock Brake System (ABS) Module

I then checked the RR wheel area and did not see any nicks or cuts to the cabling for the speed sensor. Everything in the RR area looked fine.

I have to admit that I am a bit intimidated by the apparent complexity of this vehicle.

Is it possible that some intermittent fault related to the RR wheel speed sensor is causing the "4Matic Currently Unavailable" and "Parking Brake..." messages?

Or, what could be going on here?

Thank you very much for reading this, and further, for responding if you decide to do so. We appreciate it.

sub786sub

First, try washing the connection with an electric connection cleaner spray. I found this one ( see Amazon link below). Do you think it looks like this?

CarMon225

Yes, the wire looks like that I believe. Thanks. Will try cleaning the connector.

Sammykey

[QUOTE=CarMon225;8464121]Hello and greetings to all, my whole write up disappeared. I have edited this and retyped the whole post again:

Hello. My brother-in-law has a 2015 GLA 200 4Matic with about 70,000mi. I am fairly handy but we are brand new to Mercedes-Benz vehicles.
About 2 months ago it indicated "Auxiliary Battery Malfunction", and I ordered a generic battery of the same size and replaced it (under the dash). That solved that problem.

A few weeks later the dash began indicating "4Matic Currently Unavailable" & "Parking Brake See Operator's Manual". It would come on at times and go off at times.
Recently he was driving highway speeds (70-75mph) and those messages illuminated and he pulled over and shut off the vehicle for a half hour. He noticed while pulling over the steering got stiff also. After the 30 minutes he started up again and pulled back onto the highway. The messages were still indicating and the steering was still stiff. After some time the messages disappeared. This seems to be an intermittent problem.

I took a look at his vehicle.
I load-tested the battery: It passed.
I started the car and load-tested the electrical system again: The alternator seems to pass as under load it maintained 12v.
I did notice that while idling (no load test) the voltage at the battery was at 14.6 which seems high to me, but perhaps that is normal for this model.

I then tested the parking brakes: They both appeared to actuate when commanded, and deactuate when commanded.

I then pulled OBDII codes. 2 codes displayed (which I was not able to erase):
C003A
U140C

C003A code possible causes
Faulty Right Rear Wheel Speed Sensor
Right Rear Wheel Speed Sensor harness is open or shorted
Right Rear Wheel Speed Sensor circuit poor electrical connection

U140C Code - Implausible Right Rear Wheel Speed Signal Received
Faulty Right Rear Wheel Speed Sensor
Right Rear Wheel Speed Sensor harness is open or shorted
Right Rear Wheel Speed Sensor circuit poor electrical connection
Faulty Anti-Lock Brake System (ABS) Module

I then checked the RR wheel area and did not see any nicks or cuts to the cabling for the speed sensor. Everything in the RR area looked fine.

I have to admit that I am a bit intimidated by the apparent complexity of this vehicle.

Is it possible that some intermittent fault related to the RR wheel speed sensor is causing the "4Matic Currently Unavailable" and "Parking Brake..." messages?

Or, what could be going on here?

Thank you very much for reading this, and further, for responding if you decide to do so. We appreciate it.




I have a very similar issue with this.
even after replacing my wheels Speed sensor
still same issue.