ECU change in W245 B170 CVT

[Albert28]

Hello guys, have a problem, my gearbox sometimes gets in limp mode, after restart it drives absulately fine again, on all modes, went to garage which working just with mercs and diagnostic shown ECU problem, so been told valve body needs to be changed and it costs 870£ just for part as it HAS to be brand new. Asked why cannot be used second hand one or maybe it needs just some software update or something, as it looks like that is electrical reason, not mechanical, been told that they are locked to a car and cannot be used on different one. Unless engine ECU/key/ignition changed as well as gearbox ECU.
Does anybody had (I'm sure had) similar or same problems and what is a cheapest way to sort it out?
Many thanks for any info

 

[AMGeed]

That quote of £870 for the part only sounds extremely expensive for a valve body.
I'd get a second quote.

Control unit, automatic transmission for MERCEDES-BENZ B-Class (W245) cheap order online

 

[grober]

Gearbox

 

[GLK]

Get the error codes and speak to Forrera - your garage' statement sounds really dodgy, most probably they just making it up, to cover for eventual failure to fix the problem.

As far as I know (and I'm not an expert by a long shot), there are two main reasons for similar problems: dried out soldering points inside the TCU, or a cracked valve body.
Both repairable and neither is as expensive as you've been quoted.

I do know for sure never to put my CVT in gear, until the revs drop below 1000rpm - as advised by Forrera.

 

[wongl]

Hello guys, have a problem, my gearbox sometimes gets in limp mode, after restart it drives absulately fine again, on all modes, went to garage which working just with mercs and diagnostic shown ECU problem, so been told valve body needs to be changed and it costs 870£ just for part as it HAS to be brand new. Asked why cannot be used second hand one or maybe it needs just some software update or something, as it looks like that is electrical reason, not mechanical, been told that they are locked to a car and cannot be used on different one. Unless engine ECU/key/ignition changed as well as gearbox ECU.
Does anybody had (I'm sure had) similar or same problems and what is a cheapest way to sort it out?
Many thanks for any info

See if you can get the error codes from your garage as the common CVT valve tray 'fault' shows several error codes at the same time caused by one or more breaks in the wires on the valve tray PCB going to the electrical sockets on the body. The CVT valve tray is a sealed unit containing a PCB immersed in gel and located inside the bottom of the gearbox where it is immersed in gearbox oil.

If the valve tray is showing the common fault, then it is repairable by ECUTesting for under 300GBP. If you are competent enough to drop the gearbox sump, filter and valve tray, you can do this repair yourself. Just make sure you get fresh gearbox oil, filter and sump gasket from MB when you come to reinstall the repaired valve tray.

The valve tray is coded to the engine, so a second-hand unit will not work in your car, although I would personally explore the Developer Mode in Star diagnostic where it can copy the settings from one controller to another. But it seems this needs to be done in one session as it cannot save the settings to a file to be transferred later.

MB used to sell the valve tray separately for circa 500GBP, and the new valve tray will self code to the car after twenty engine starts. For some reasons MB has stopped selling the valve tray separately for some time now so repairing it is your only economical avenue (unless you can succeed in using Star Developer Mode to clone the settings in your valve tray to a second-hand unit - also there is no way to confirm if the second-hand valve tray is faulty or not).

Here is a short write up of my experience back in 2015 for my W169, but the W245 shares the same gearbox and controllers - w169-auto-transmission-fault.191266