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

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That's a whole load of info

You've seen the sticky post in this section on where to get repairs? lot of good options listed their. I posted details in that thread about a Turbo Repair place (I realise the turbo isn't this issue) Aziz who runs it is very helpful and speaks good English so might be worth a call to see if he knows who can help. He also has connection with Ali Nassir in Zagora

Hi Ryan:

I'm not familiar with Mercedes products, but I am very familiar with Volkswagen products, and they use a very similar system for ASR, ABS, and ESP.

My suggestion is that you just ignore the problem until you get to some location (perhaps a big Moroccan city in the north, or perhaps even back to Europe) where you are comfortable and confident that you can get the problem fixed.

There is nothing mechanically "wrong" with your vehicle. As you have determined through your own investigations - and it sounds like you know what you are doing, and what you are dealing with - you have suffered a loss of functionality of the above-mentioned safety systems. That's all.

Before I retired, I was an aircraft pilot and aircraft maintenance technician. All large aircraft have what is known as a "Minimum Equipment List' (MEL). When a component or system fails on an aircraft, it doesn't automatically ground the aircraft. The pilot looks up the failed system on the MEL, and the MEL provides guidance about whether or not the aircraft can continue to be safely used with the inoperative component or system.

If your Sprinter was an aircraft, I suspect the MEL guidance for your particular system failure would look like this:

"Vehicle can continue to be operated until reaching a service facility, but anti-lock braking, stability control, and wheelslip regulation will not be available. Avoid operation on sandy or slippery surfaces, and be aware that one or more wheels may lock up if hard braking force is applied."

In other words, take note of your failure, don't go down roads that you wouldn't travel on with an ordinary passenger car, and be aware that you no longer have ABS protection. But otherwise, continue your journey as normal.

Michael

I'm with Michael - just drive round it until you get to a place where it can be sorted out at leisure. I've had similar issues with my Land Rover over the years and while it's nice to have these features they're not trip ending if they go wrong. It would be an MOT failure in the UK but as long as you're not heading for a test centre and there's no mechanical failure causing it fix it later.

As the OP says the intention is to continue south, just "driving it 'till they find somewhere better" might not be an option - Namibia? I would guess running back up to Casablanca would be a better bet.


http://www.autonejma.ma/

Better to back track to a Merc specialist than ploughing on south, worrying all the way if it's going to get worse.

Get it sorted now, lose a couple of days and enjoy the rest of your trip.

Happy trails,

Peter

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Here's a link to a list of Mercedes dealers in Morocco - if it is important to you to get the problem fixed before you carry on, the closest dealership is in Agadir.

Mercedes Dealerships in Morocco

Laayoune, just south of the old Morocco - Western Sahara border, is a pretty thriving place. I was there a year ago, and the town is an economic powerhouse. Although there are no Mercedes dealerships listed in that town, I am pretty sure you would be able to find someone with sufficient competence to repair your vehicle there.

Getting parts shipped from up north (Casablanca, etc.) is super-easy - see this post I made last year, when I got stuck with my moto not too far from where you are now and needed parts shipped to me: Awesome Parts Delivery Service in Morocco.

Michael

I was going to support the suggestion that Laayoune - and Dahkla - are bustling towns with many garages. And there's surely a dealer in Dakar!

Then I came across a Merc dealer in Agadir - listed on an official website, here. Only passenger cars mentioned.
Sud Star Auto SARL
70 Av 11 Janvier - Cite Dakhla
Agadir
Morocco
Phone: +212 5 28 23 98 32 Fax: +212 5 28 23 98 33

Oddly, the Dakar entry I saw isn't included in the same list
La Sénégalaise de l'Automobile
BP 3828 - km 2.5 Boulevard du Centenaire
Dakar - SENEGAL
Tel.: +221 33 849 38 27 Fax: +221 33 849 38 45

You may well ask .. shouldn't I be planning my own trip?
Bonne route !

[Edit] Just re-read the post and noticed you were already aware of the Agadir dealer.

Thank you all for your suggestions. We don't want to continue down into Western Sahara or Mauritania with this issue. My husband is an electrical engineer and is trying to troubleshoot the issue. Per the MB dealer in Agadir, there are no wheel speed sensors in Morocco. My husband is not convinced it is actually the speed sensor.

Per my husband:

Today, I again measured 12V to both the right and left rear wheel sensor's connectors (located in front of the rear axle) when the connectors were unplugged and the ignition was "on". This is a good indication that the wiring harness is ok, but does not preclude a "high resistance or poor connection" at the sensor socket. I did move the connector pins around a bit in case their mating socket was a bit off.

I also swapped the right and left sensors by slightly modifying the "keying" of the connectors. I can now plug the left sensor into the right wiring harness connector and vice versa. This test caused the iCarsoft MBII plugged into the ODB2 port to report a left AND right rear wheel sensor failure. My theory there is that each sensor has a CAN digital address that is read by the Sprinter's electronics and a fault is indicated if the address is incorrect. Can anyone confirm my theory? (Note that we did not attempt to drive in this sensor-swapped condition.) My hope was that these sensors were purely analog sensors and when the left and right were swapped, I would get a failure on the "new" left sensor instead of the original right sensor. Now that both sides have faulted, I call this test inconclusive.

After messing around with the above and clearing the check engine light, the three dash lights referenced in my first post stayed on. We then drove the Sprinter about 25 miles to fill up. After the engine restart, the three lights went off after a few minutes driving. Two hours of continuous driving later, they came back on.

We did manage to get to the Mercedes dealer in Agadir today. They said there are no wheel speed sensors in Morocco and it could take 25 days to get one from Germany.

I would like to try Dennis's idea about piggy backing wires from the sensor to the ABS brick. I'll see what materials I can scrounge up tomorrow. It would also save a lot of time if I could come up with the ABS brick's pinout. Otherwise, I will need to "ohm out" the entire connector.

Thanks for the help so far!

Are the sprinter sensors fitted to any other vehicles? could give you another option to find a replacement.

Might be worth checking the scrap yard at Ait Melloul for 2nd hand spares. It's just next to the N1 by the turning for the airport.

Busy season starts over the next few weeks so there will be a lot of people heading to Morocco from Europe, might be able to find someone to bring one

Get 1 delivered to you in Morocco? this could take a couple of weeks but probably faster than waiting for Mercedes to get one.

I'll be in Morocco on the 9th and could bring a sensor with me. But I won't be down in the south until the end of March as we are exploring the Rif and the med coast for a couple of weeks first

It's not just a wheel bearing going is it? Land Rover Discovery abs systems start flashing before there is much discernable play. (I don't own one, just mend them. It's a full time job!)

Is there a part number on the sensor? Or could you get the OEM part number from the Agadir dealer.
Then cross-referencing on the web might turn-up other vehicles that share the part.

My breakdown cover woukd ship parts to me. I'm with ADAC, but you might have similar.

I thought Mercedes had a good worldwide reputation fur afterservice?

I have no experience with Mercedes vehicles, but on all Volkswagen vehicles, the speed-sensor is a simple analog device (Hall effect sensor) that is wired to the ABS controller. Each wheel has its own wire leading to its own pin on the ABS controller. I doubt very much if wheel speed-sensors on any vehicle communicate via the CAN bus, simply because there isn't enough bandwidth on an automotive CAN bus (even a high-speed one) to cope with 4 different sensors reporting at the same time. Contemporary ABS systems operate at about 50 Hz - to get reliable reporting from speed-sensors, they need to have a direct (analog) connection to the controller.

In light of the unlikeliness of two sensors failing at the same time (in the absence of some event to explain this, such as immersing the back end of the vehicle in water or similar), I think you might want to start suspecting that the controller itself is at fault, or that you have a fault in the wiring harness leading from the rear of the vehicle to the controller.

Do you have a detailed Mercedes wiring diagram (schematic) for the ABS system on your vehicle available to you? If not, perhaps try and get one, that would show you where the various connections are between the sensors and the controller, and enable you to inspect the connections and search for faults there.

The fact that you have an intermittent fault condition (after clearing the fault codes, you were able to drive for two hours before the faults returned) suggests to me an increase in the probability of a wiring fault or controller fault. In other words, the two sensors performed satisfactorily during that two hour period - to me, that diminished the probability that one or more sensors are at fault.

Michael

I’m no great technician but I’d suggest you consider taking it to Ali Nassir in Zagora (whom The Warden mentioned). I was there last week and as usual they were dealing with a massive range of vehicles.

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