W212 transmission problems

[mshah70]

Looks like a faulty conductor plate/TCU (on the same thing inside the gearbox).

There are some places that replace just the faulty speed sensors but I have no experience with then.

Its a theft relevant part so needs SCN coding in with Online Xentry.

Do i need to replace whole TCU or just the conductor plate?

The error code doesnt always show up, it showed up on snap on diagnostic as gear 1, gear 2 slipping, while nothing showed on star.

But when the engine management light came on, the codes came up as shown above on Star.

 

[alexanderfoti]

Do i need to replace whole TCU or just the conductor plate?

The error code doesnt always show up, it showed up on snap on diagnostic as gear 1, gear 2 slipping, while nothing showed on star.

But when the engine management light came on, the codes came up as shown above on Star.

On the 722.9 they are the same unit.

Unless you have a feeling that the box is actually slipping before it goes into limp mode.

 

[mshah70]

On the 722.9 they are the same unit.

Unless you have a feeling that the box is actually slipping before it goes into limp mode.

My one is 722.6
Sometimes it happens while driving, the revs would slow down and go into limp mode.
But more often than not, i cant feel the slip, it just doesnt engage even while stationary.

 

[alexanderfoti]

My one is 722.6
Sometimes it happens while driving, the revs would slow down and go into limp mode.
But more often than not, i cant feel the slip, it just doesnt engage even while stationary.

Ah, in that case you can just replace the conductor plate. Although you may want to check that oil hasn't wicked its up the cable to the TCU. If you unplug the cable from the TCU (not sure of its locaiton on your car) and look to see if it has oil in it. If so, I would replace the pilot bush first.

 

[mshah70]

Ok il check on that.

My question is, if it’s something to do with tcu/ conducter plate, shouldnt it show up in star all the time.

When i scanned the car a few times using star
Nothing showed up Until engine management came on. However when i scanned with snap-on tool, the codes showed up.

 

[alexanderfoti]

Ok il check on that.

My question is, if it’s something to do with tcu/ conducter plate, shouldnt it show up in star all the time.

When i scanned the car a few times using star
Nothing showed up Until engine management came on. However when i scanned with snap-on tool, the codes showed up.

Yes, I would have thought those codes would have been present the whole time.

Did you clear all the codes in the interm perhaps?

 

[mshah70]

Yes, I would have thought those codes would have been present the whole time.

Did you clear all the codes in the interm perhaps?

No i didnt clear the codes

 

[mshah70]

Ok just had a look at the tcu under the passenger side footwell, its bone dry

 

[NEIL SPOONER]

All gone quiet.......What did you do to cure the fault?

 

[ajlsl600]

View attachment 44175 Guys the problem has started again.
While ATF is cold the car drives ok, as soon as ATF fluid warms up the car doesn’t engage in gear.

Im really puzzled.
If anybody can help itl be great

Leakin past seals ,valve seats when oil hot. Valve seats,solenoid s are a possible fix,seals a likely trans overhaul start by finding out HOW oil became low in first place,if not careful one walks past the origional cause.

 

[Wighty]

All gone quiet.......What did you do to cure the fault?

He hasn’t been on the forum for 2 years buddy , start a new thread to get better help

 

[NEIL SPOONER]

Thank you.......just watched this video on youtube.......looks like my next job!

 

[Wighty]

Thank you.......just watched this video on youtube.......looks like my next job!

What mileage are you on now ?

 

[NEIL SPOONER]

137000 miles.
The symptom I have is RPM surging at light throttle, about 1500rpm when the engine and transmission is cold/cool....once hot its fine apart from the occasional poor shift change. I thought it to be an engine issue, but from observing this fault for a while am now convinced that the g'box is "hunting" it's next upchange, once it's shifted up a gear it's ok. You can see the rpm fluctuating about 200rpm and feel it through the car.
I changed the g'box oil & filter with genuine MB parts about 1000 miles ago.

 

[ajlsl600]

He hasn’t been on the forum for 2 years buddy , start a new thread to get better help

Yeh noticed that after my post.wot t do?