Andy Turner

I get the message ''Diff Lock overheated'' usually after mild wheel spin on acceleration. I very much doubt it is actually overheating as it can occur from a cold start. This message has only started appearing in the last 2 months and first became apparent the day after I changed a rear wheel speed sensor which was also the fist time I ever drove in the car in snow. While the message is on the diff lock control is disabled. It comes back on within a minute. I have tested the diff lock by selecting the different modes on the control and it seems to work ok. There is no unusual transmission noise. I have cleared fault codes using icarsoft tool. The message doesn't really cause me a problems, but I'd like to get to the bottom of it. Any Ideas?

James Serridge

Hi mate

I'm having exactly that same issue. Only every now and then after a rough road or pothole. Sometimes after driving in the wet with a mild wheelspin.

Did you find the answer?

cheers

James

Andy Turner

Hi James,
you are the first reply. I still don't have the answer. I changed both diff fluids, nothing changed. Slightest wheel spin causes the message. Not really a problem just annoying.
Andy

Jimbo1234

Hi mate I've solved the problem. I'm username James serridge but cant login to that account. Change all 4 wheel sensors to upgraded ones. Must be merc parts. It has cured the diff message and hillstart assist . James

Andy Turner

Hi James,
Thanks for the promising reply. Firstly what made you buy 4 genuine sensors as they are very expensive, why did you think this might help? What are upgraded sensors? Did it solve any other issues. I don't want to spend £500 on sensors in case it doesn't cure my problems. Are you able to offer more reassurance.
Cheers, Andy

Jimbo1234

Hi Andy.

If you're having diff overheat message and hill start that jams on as you start pulling away its definitely the sensors. My car was at the main dealer and the master tech was taking care of it. He knew the solution straight away. He mentioned 4 updated or upgraded sensors and he reset something. Paid for by third party warranty company called motoreasy. They also replaced a mirror that was folding in too slowly .

Andy Turner

Thanks James, sounds convincing. I'll look into the updated sensors. Andy

Andy Turner

just fitted 2 genuine abs sensors. Everything works ok now. Many thanks. Andy

Andy Turner

Yes, removed 2 aftermarked abs sensors and fitted genuine mb ones. Everything works now.Andy

Roosterman17

This is very useful; I have the same problem with the 'Diff lock system overheated' message coming on every time I drive on a dirt road, and the hillstart assist abruptly braking the car (in forward or reverse) when moving away from a stop on a slope. I'll get the wheel sensors checked out. Thanks

expl0rer

I had the same message come up and was related to wheel sensor (I had issues with low battery at the same time too, which resulted in a pile of codes being thrown). Replacing the sensor and charging the battery fixed mine. I went with aftermarket sensor, IIRC Delphi brand and only replaced the one failing, rather than both on the same axle. I wanted to test how long the other would take to break. In the thread where I posted, it was suggested that the low battery may have been the cause of the wheel sensor bombing. This was in the summer of 2020 and I so far so good.... and I just jinxed myself lol

Max Blast

yep - that was mine; I had a battery go out and very shortly after replacing it burned a rear wheel sensor.
A failing wheel sensor will in a non-EORP car (ancient OP has the off road package) just trigger the ESP and ABS warning messages.

in most cases the steering will become very heavy because the variable speed variable effort power steering solenoid trips offline.

with EORP you’ll have another layer of faults related to the rear diff lock as well.

Jimbob442

For anyone reading this thread with the same problem, mine was the exact same, diff overheat message, ABS / ESP warning lights and even “crabbing” when turning ever so slightly, turned out to be a bad rear wheel sensor, installed and driving great again (GL350 CDI 2011)