Hello all, i believed all the W245 & W169 owner may have experience before in facing this "Transmission Visit Workshop" error. The error might be able to be temporary cleared by restart the car, but the error will come back more and more frequent over time.
Here i would like to share my experience on repairing this transmission error.

first, when "Transmission Visit Workshop" error display occurred, you may getting these error code description after connecting OBD2:
0717 The RPM signal from component Y3/9b5 (CVT output rpm sensor) is not available
0720 Speed Gradient nPrimGrd > nPrimGrdMax
0722 The RPM signal from component Y3/9b5 (CVT output rpm sensor) is not available
0723 The RPM signal from component Y3/9b5 (CVT output rpm sensor) is implausible
Etc
(i can't remember all because it was 1 year ago when i have it repaired)

All these are related to two speed sensor wire in TCM (Transmission control module) that has been opened due to long time heat and vibration. the photo as below are the opened wire:




My sincere advice is "DO NOT REPAIR THE TCM BY YOURSELF". the reason is these wire is aluminium and you can't do with normal soldering. The normal soldering lead will not join these wire. you need special "Alusol" solder wire to solder it properly. Moreover, once you cut open the casing, you need to properly melt solder back the plastic cover. This required high skill to handle.

Like my case, the easy way is to order a recond TCM from aliexpress. The link is as below:
Original TCU/TCM 722.8 CVT Tested With Programming

What you need is to provide the seller your car's VIN number for them to do programming to match to your car.

I paid around RM2300 for this TCM inclusive shipment. I have also checked with Authorized part dealer and knew that the new one cost around RM9500.

Then, you need to find a reliable workshop to replace this TCM. The fee is around RM1K ~RM1.5K. (replace original CVT oil, filter, gasket, clear error..) Remember to collect back the old TCM after repair for your hobby.

Upper is the old broken TCM and bottom is new one bought from aliexpress:


So that's all, my baby benz came back to life again.

Someone might have doubt why i didn't find the second hand one locally. I think all these TCM have design fault and prone to fail over time (because of these two broken speed sensor wire in TCM). if unlucky, you might face same failure within a year after replaced with used one. The used one has no warranty by the shop. So, i bought from this seller because they claimed have it recond to strengthen the wires.

*The above sharing is based on my case only and it might not works for yours. You have to judge it yourself and take full responsibility on your own.*