722.6 Speed sensor/conductor plate

[m3gt2]

It should be just that as I have never seen another thread where it has been anything else. It is the speed signal part that gives the problems.

Sorry, 1 last question, have you know the plate to fail but not show any fault codes on Star?

 

[television]

Sorry, 1 last question, have you know the plate to fail but not show any fault codes on Star?

Yes, this is often the case.

 

[bed_sat]

Sorry, 1 last question, have you know the plate to fail but not show any fault codes on Star?

AS TV says, yes this can happen - and the conductive plate is more likely as anything to need changing.

I would still swap the TCU first just to check it, though - it's not going to cost you anything and will eliminate it as a potential cause of the problem

 

[AdamG]

One potential issue with swapping the TCU is the gearbox adaptation data will be for a different car. Ideally it should be reset with STAR but it will probably relearn quite quickly.

 

[m3gt2]

I'm a little confused now! My mechanic said that the TCU are coded to the car so I chec with Mercedes parts dept, who asked the workshop for me, and they confirmed they need coding? I don't mind unplugging to try but am worried about recoding incase anything goes wrong and I'm left with 2 cars playing up!

 

[television]

I have never seen a thread where the ECU has been a problem

 

[m3gt2]

Thanks Malcom, if they were swappable it was just an extra way to narrow the fault down without expense lol but I do think it will be the plate the more I read and hear!

 

[television]

The plates come up on STAR in the event of a complete failure of the speed sensor part. If you want to swap the ECU you can do so, it will do no harm,but it could prove the point, you could put the original one back in and all as it was.

As earlier with the tiptronic box you do have the ECU in the shift housing, and it is this one that drives the display.

 

[AdamG]

I'm a little confused now! My mechanic said that the TCU are coded to the car so I chec with Mercedes parts dept, who asked the workshop for me, and they confirmed they need coding? I don't mind unplugging to try but am worried about recoding incase anything goes wrong and I'm left with 2 cars playing up!

You can definitely swap TCUs provided they are both from the same model and engine. I just put one in my car that was from an 05 w220 320cdi into my 03 w220 320cdi.

I think the problem arises if swapping from a different model and or engine. Your mechanic maybe thinking of the 7g box which some W220 have which is coded to the car.

 

[m3gt2]

The plates come up on STAR in the event of a complete failure of the speed sensor part. If you want to swap the ECU you can do so, it will do no harm,but it could prove the point, you could put the original one back in and all as it was.

As earlier with the tiptronic box you do have the ECU in the shift housing, and it is this one that drives the display.

Could a faulty shift housing cause these problems then or is that just the display and physical lever movement?

 

[television]

Could a faulty shift housing cause these problems then or is that just the display and physical lever movement?

I do not know that much about these, they do have electronics in them as when faulty the display shows ---- and the box locks up in P, they could fail in other ways, but I do not know any more about them.

 

[m3gt2]

Well the engine cut out twice this morning when it was put in gear. Should be getting the plate changed on Monday, fingers crossed!

 

[television]

This plate cannot cut the engine as far as I know, its more like an engine problem and power down.

 

[m3gt2]

Well, I hope you are wrong on this lol. That makes it 3 times its done this in a month or 2. Every time has been at low revs, in gear and when the engine was still cold.

 

[m3gt2]

Thought I would update this. Had the plate, plug, filter and gasket changed. Got the kit from One Stop Gearbox Shop on ebay for £150 and the plate has Mercedes part number on so would seem genuine. It seems to have cured every problem except that manually changing down always goes D-4-3 etc regardless of which gear you are in. Would be nice to sort that but if I cant I will live with it!

 

[whitenemesis]

You are limiting the gear range, not changing down. The car will only down-shift when it is the acceptable rev range.

 

[m3gt2]

You are limiting the gear range, not changing down. The car will only down-shift when it is the acceptable rev range.

I know but the others that I have owned, and I'm sure this was the same, if for example I was driving in D and the box was driving in 3rd at 30mph and you hit - it goes from D to 2 in the display, and drops the box to 2nd. Same situation in this car now and the D would change from D to 4 and then hit - again for the display will show 3. Only on the next - will it drop to 2nd?

 

[television]

I wonder if you have a tiptronic control ECU playing up, they are temperamental things

 

[m3gt2]

I wonder if you have a tiptronic control ECU playing up, they are temperamental things

I have no idea, would it not show up on Star? No faults showing?

 

[television]

Normally yes unless it is an unplausible fault maybe, too hard to be sure.