Real Time Help: Morocco

[Chickadee]

My husband wrote the following. Any information would be appreciated.. We are currently about 2.5 hours South of Agadir. We are attempting to contact Sudstar Auto in Agadir to see if they can assist us.

My wife and I are traveling through Morocco and hope to head further south into Western Africa with our 2018 144” high-roof 4X4 Sprinter:

At this point, I’m don’t think we want to proceed without at least understanding the issue below or fixing it.

Two days ago, we got these three amber warning lights on the dashboard: ABS, spinning wheel (ASR/BAS), and swerving vehicle (ESP). After a while, we also got a solid amber "check engine light”.

Other than the cruise control not working, everything else seems normal.

Our UltraGauge ODB2 reader stated that the engine code was “C003A”. An internet search seemed to say that the right rear wheel speed sensor was at fault.

This confirmed my gut suspicions as to what (wheel speed sensor) and where (right rear) since we have had two instances in Iceland and Germany where the rear right wheel has been spinning in river gravel during a water crossing and in a muddy ditch, respectively. Each of these instances caused damage to the tire’s valve stem.

At this point, I was hoping a thorough cleaning of the wheels and undercarriage would alleviate the problem since we had just crossed the High Atlas Mountains over a few days and 200 miles of dust, dirt, mud, and snow. After a high-pressure wash, the lights remained on.

The next day, I broke out our iCarsoft MBII and it notes: “CAN bus - CAN signal 'Rear right wheel speed' from control unit N 30/4 (ESP control unit) is missing or faulty.”

Next, I located the sensors and disconnected the closest connectors that are attached to the body/chassis just forward of the rear axel. At each connector, I measured the voltage at about 12.0V coming from the electronics side of the connector (side going towards the engine bay to the control electronics). Knowing nothing more, this indicates that the wiring and electronics from the Sprinter are ok.

Now, it was time to focus on the sensor side. In doing internet research on the issue, it seemed that the wheel speed sensors could be Hall effect and not the old-school, simpler magnet type. So, I did not and have not “Ohm'ed out” (measure the resistance of) the sensors.

Next, I decided to take the wheel off and clean as mush as I could without doing any “invasive” disassembly. I was able to disassemble down to the rotor and parking brake shoes.

At this point, I was a bit surprised to see that I was unable to get down to the “tone ring”. This is the gear-shaped ring that coupled to the old magnet-type sensors. The sensor on our Sprinter seems to be included in the “hub assembly” for lack of better terminology. I am not up to the task of taking it apart further without more information…

After pulling the wheel speed sensor, I was able to somewhat clean the "spinning part” (analogous to the tone ring) with Q-tips down the sensor tube. I also cleaned the sensor and added back new, clean Lithium grease. We also inspected the sensor cable and all looks “like-new” with the exception of road dirt on the cable.

After reassembly, I was able to clear the codes for several miles. After a subsequent engine re-start, the warning lights all came back.

Now, what to do next…

It is not clear if we can get a “full service” Mercedes dealership and repair facility in Morocco. Even if we can, I’m not sure what the real issue is - sensor or “tone ring”.

What I would like to do next is to swap the left and right sensors. My thought is that if the control electronics now say the new left sensor is at fault, the current right sensor is to blame. If the error remains on the right, the right “tone ring” can be to blame. I have not tried this yet.

Here are my questions:

1. Are the right and left wheel speed sensors the same?
2. Are the speed sensors indeed Hall effect-type?
3. What is the “tone ring” called?
4. What is the rough procedure for getting at the “tone ring”?
* Looking for things like: "take out the axle", "disassemble the hub", etc.
* I want to know if this is something I want to tackle in a small town or the bush.
5. For you experienced Sprinter mechanics, is this likely a sensor or “tone ring” issue?
6. Also for you experienced Sprinter mechanics, is a cleaning of the “tone ring” likely to fix the issue?
7. Is there anything more I can do to troubleshoot this?
8. Is there a wheel sensor check procedure?
9. Anyone know of a good Sprinter mechanic near Agadir, Morocco?

I have learned quite a bit on this forum over the last year and a half while building up on vehicle. In fact, I have mostly been able to answer my questions just by reading the archives and not needing to post. So, thanks for all your help!

Thanks,
Ryan