Limp mode after rough downshift but no error code

[chris116]

W211 MY2005 7 speed auto. I have an occasional issue that now appears to getting more regular I feel it's gearbox related but could be wrong. The car will occasionally enter limp mode but stopping turning off and restarting clears the fault this is now occurring from what was a couple of times a year to now about every couple of weeks. The fault is either there shortly from start up or not at all it has never occurred after running fine during a journey and has always cleared by restarting. My local garage does all the work and cant find any fault codes but he does not have STAR. He found a turbo related fault code once but I don't think they are connected.
The symptoms appear to be the car pulls clean off the mark then holds back with limited speed and power it's not noticeable in slow traffic. The only indication of the fault about to occur is the down shift seems to start feeling rough sometimes jerky approaching a stop I also think I occasionally noticed the revs climbing as though its been a bit slow on the up shift a couple of times. Apart from the occasional rough down shift the gearbox feels fine and shifts smoothly in auto & manual when in fault.
Any ideas?
Many thanks in advance for any help or suggestions
Chris

 

[zipdip]

These boxes need regular oil changes,has yours had a oil change,the electronics can sometimes give a problem,changing the speed plate or repairing it may be a option,it is one of the strange things that the faults you post sometimes do not leave a fault code,I would get a indy to look at it and change the oil,post where you are and somebody will recommend a good one near you

 

[chris116]

These boxes need regular oil changes,has yours had a oil change,the electronics can sometimes give a problem,changing the speed plate or repairing it may be a option,it is one of the strange things that the faults you post sometimes do not leave a fault code,I would get a indy to look at it and change the oil,post where you are and somebody will recommend a good one near you

I think all is up to date according to the service book. The PO was a garage owner who did all the work himself. A mate of mine also a garage owner ex Rover main dealer now does the servicing but not done gb oil. The PO stipulated the gearbox oil change should be carried out by persons with specific MB experience & knowledge any reason for this?
My location is Sheffield S21 area between Sheffield Chesterfield & Rotherham

 

[Peter103]

When I had a similar problem with an E220. still under warranty, I was told when it next happens don't turn the engine off, if you do the fault code will be lost, take it to the nearest main dealer and they will connect it to their computer, I did, they put it down to the gearbox software, and reprogrammed it, however within a month it happened again. I eventually returned the car and took another. So my message is, don't switch off , get it checked first.

 

[zipdip]

Well the 7G box does not have a dipstick,there is a set way of changing the oil and refilling it,plus the filter will need changing plus all the sump bolts will need replacing as they are once only's,always use a good Indy,I am in Essex so have no idea of indys in your area,I will say there is a company who will remove the speed plate and put it on a machine to check every function and repair any that are not right,they are near Liverpool,the name escapes me for now but a web search should reveal them,but it might not come to that get to a indy recommended on here.

 

[chris116]

Well the 7G box does not have a dipstick,there is a set way of changing the oil and refilling it,plus the filter will need changing plus all the sump bolts will need replacing as they are once only's,always use a good Indy,I am in Essex so have no idea of indys in your area,I will say there is a company who will remove the speed plate and put it on a machine to check every function and repair any that are not right,they are near Liverpool,the name escapes me for now but a web search should reveal them,but it might not come to that get to a indy recommended on here.

Think these may be the guys you mean, I'll give them a call.
Are there any instaces of an intermitent speed sensor fault resulting in a total failure? turning off then back on is much quicker and cheaper than a new valve body!!!

Valve Bodies UK LTD
Robbs Garage
Claremount Road
Wallasey
Merseyside
CH44 2BW

 

[zipdip]

Think these may be the guys you mean, I'll give them a call.
Are there any instaces of an intermitent speed sensor fault resulting in a total failure? turning off then back on is much quicker and cheaper than a new valve body!!!

Valve Bodies UK LTD
Robbs Garage
Claremount Road
Wallasey
Merseyside
CH44 2BW

Thats the guys,they say once you have a booking you can drop it off and it will be ready the same day,the reason I mention them is for the last couple of years there has been a solution,of owners sending the faulty speed plate to Bulgaria,by post and getting a very cheap repair,it is returned in a week,I know it sounds crazy but seems to work well,of course there are some Indys who will do the job as well,I have been looking on the site and Sheffield seem to have no recommended Indys,I am amazed.

 

[nathanrobo]

The 7G Tronic box has had a number of adaptations - I understand that MB have released some experimental code to dealers and that some of this code masks the problems of the control module, so that owners won't see it (if this is the case it's classic case of big corps trying to manage brand perception and prevent costly recalls).

So best to get the car put on Star, have codes read and have the box 'live read'.