W203 722.6 Gearbox Woes!

[FairEnough]

Hi all!
Having some issues with my w203 C220 CDi... the gearbox is playing up and is stuck in a limp mode situation. When you go into reverse or drive it jerks which tells me immediately something up. After doing some research I decided to change the conductive plate however this hasn’t made any difference.
I haven’t got anything to check the codes and can’t get it to Mercedes’s. Interesting thing is that the selection display on the dashboard says it’s on D no matter what gear it’s in, it also won’t change into manual either. Any ideas? Could it be the shifter module?

Any help is greatly appreciated!
Thanks

 

[AltonAnt]

Have you checked the electrical connection? The seals eventually allow fluid in to contaminate the connections?
A new part is around £10 and fairly straightforward to replace.

 

[FairEnough]

Which connection did you mean? I have replaced the plug by the gearbox sump when I replaced the conductive plate if that’s the one you mean?

Currently have the shift unit out from the centre console and giving that a spray and clean out in the hope it might help!

 

[Joesoap17]

Until you read/clear codes it may still act up, try a hard reset-battery disconnect,
but you could have an engine/ecu problem that is upsetting the gear changes or engine/trans mount issue?
Have you thought about buying a decent code reader?

 

[cws196]

Or worse-case ATF has migrated up the loom from the leaking pilot-bush seal. Either way you’re completely stabbing in the dark without having fault codes read.

 

[FairEnough]

Well i put it back together and it didn’t want to play ball but if I disconnect the shift unit and reconnect it again by the plug on the module it works as it should... drive it around for about 20 miles and then it decides to go into limp again. I’ve got a basic OBD reader that bluetooths to an app on my phone but don’t know if that’ll be any good with the Mercedes system?

Truth be told the car has had this problem for best part of a year however I’ve had it parked up as I didn’t have time to look at it myself. When this first happened it went to Mercedes and even themselves couldn’t say what the fault was and wanted to charge me excess of £3k to put it right and even then they couldn’t guarantee it would work!

 

[FairEnough]

Just tried my cheap OBD and it’s pulled a P0705... Seems to be a lot of different suggestions with this code on the forums but most say “P0705 Transmission Range Sensor Circuit malfunction”. Someone give me some good news on what that might be! Haha!

 

[Jimmas]

Not 100% sure but I think it relates to the Transmission gear position switch, which I think is on the outside of the box somewere, hopefully someone with more knowledge will be able to help.

 

[Joesoap17]

think it points to shift module in centre console, but have you tried a good indie?

 

[Snoop108]

If fluid has been spilled around the gear shifter area or even steam cleaning, it can freak the selector out. Selector module might need changing. I had this issue after a valet. It literally doesnt know what gear its in, so it goes limp and wont select. £60 for used on ebay

 

[Petrol Pete]

You opened up your gearbox and replaced the conductor plate before have the codes read by a decent OBD unit ???

Boy oh boy , are you going about this 'asre about face', but I admire your bravery. And having said that by the sounds of it and with some help from this forum you will probably end up fixing it by the simple process of elimination.

Good luck and keep us posted on the result.

 

[markjay]

If you can't get the car on STAR.... then you may need to fork-out for a basic Mercedes scanner, e.g. iCarsoft MB v2.0 (Standalone) or Carly for Mercedes (Bluetooth).

This will allow you to read the MB-specific TCU and ESM fault codes (on top of the standard/generic OBDII ECU/TCU fault codes).

Unless you are happy to get a second-hand ESM off eBay and replacing it, in the hope that it might cure the problem.

 

[FairEnough]

Thanks for the reply’s guys - Am being a tad brave I know and unfortunately haven’t got anyone near to me that has a decent star machine I can get hold off (MB dealer is a a fair few miles away and has already seen the car).

Have been thinking about buying a decent OBD reader as my hope with it being a ‘simple conductive plate issue’ has gone haha! I’ve managed to get hold of another transmission ECU (the one that sits in the footwell) for free and will fit that and see how it goes (as it’s free I thought I might as well give it a go! - I’m guessing this needs to be programmed in though?) I’m still leaning towards the gear shifter itself as the main issue however!

 

[classiccarzone]

you will not get anyplace unless you first clear any codes in the TCM.... and disconnecting the battery will not clear codes in the TCM.

A simple matter of starting the engine with the pilot bushing plug disconnected will cause a code that can only be cleared with a diagnostics such as icarsoft MB2. They can be bought for £136.00.

I had the problem of car going into limp mode and it turned out to be wires in the Pilot bushing to TCM loom that became brittle from the heat of the exhaust.
That code points to the position rang sensor but that may have been thrown up because you disconnected the plug.

Clear the code and see if it returns.

 

[Joesoap17]

where are you based? there are members with code readers willing to help so put your whereabout in signature it does help!

 

[andy27168]

Hi,
If you are within travelling distance of Southampton I could pop it on my STAR if wanted.

 

[Dan2k7]

Hi did you manage to fix this issue? The 722.6 box in my partners ML270 is playing up. I changed the pilot bush, filter and fluid about 6 months ago.

All was well but now it’s stuck in limp mode and sometimes won’t move when in drive.

 

[Chatters300]

I had the same issue..... 2007 C220cdi, every 100 or so miles would flip in to limp mode.... ignition off waited a few seconds then started up and fine, for another 100 miles... one day it just did not want to reset.
Jerking when in reverse, limp mode max is like 30mph which sounds horrible.

Changed both the wiring loom as fluid was already inside and slightly leaking - seals go, and the internal selector plate, new filter and fluid.
I believe the selector plate has to be re-programmed also......
not had a single problem since.

 

[Joesoap17]

I think Chatters is referring to the electroplate attached to the valve body, they can go bad but need to read codes to make sure.

 

[MLSVIPER]

Hi guys, I have a "similar" problem but mine is a bit weird! Has anyone experienced the same issue???

If I start the car in "C" mode, I will have the same issue described by our colleague on this post, gearbox will get stuck on the 1st gear, I will not be able to move the gear all way up, only to Neutral, the only way to put it on Park is to switch off the car. The WEIRD think is that if I switch on the car and choose the "S" mode, my MB will rum smoothly as usual, no issues, no gear stuck, and so on.. I did this test many times but don't know what can be the problem?

SO far, I have replaced my battery, I put I new one with the same specification. I you connected a scanner via Bluetooth and ran all APPs that I could find available. At the beggining, it was showing P0705 (transmission range Sensor "A" circuit) but I managed to clear it. If a drive in S everything stays okay but if I move to C all issues come back to life, any advice?

Thank you in advance!!!