E320 - w124 - 1994

[colinspain]

I have a 1994 E320 W124 Cabriolet which has a 5 speed auto box. It changes through the gears fine but moves very quickly to 5th. The S-E switch is not working. I have pulled out the centre console and can see the S-E switch appears to have a mechanical link. ? There are no electrical wires at the switch itself. Also nothing changes when you move the gear lever across the gate from D<>4 This also seems to be mechanically linked to a pair of contacts with a two wire plug connected. Moving the gear lever across the gate from D to 4 makes and breaks the contacts. Manually moving the gear lever from 4th to 3rd to 2nd works as it should. So it's a problem with the S-E switch and D<>4 on the gear selector. Any ideas please ?

 

[bolide]

What happens when you use the D <> 4 switch above 50 mph?

Nick Froome
the independent Mercedes Estate specialists

 

[WDB124066]

Upchanges to 5th occur at an indicated 62-3 km/h in both of mine if that is any help, too soon for my liking but there you go.

The difference between S & E on the switch is best felt when travelling at speed, the kickdown happens with less throttle travel/input in S mode, it is very subtle and I didn't notice it 'till I thought the trans was playing up one day.....

 

[colinspain]

Upchanges to 5th occur at an indicated 62-3 km/h in both of mine if that is any help, too soon for my liking but there you go.

The difference between S & E on the switch is best felt when travelling at speed, the kickdown happens with less throttle travel/input in S mode, it is very subtle and I didn't notice it 'till I thought the trans was playing up one day.....

Thanks but there is no change above 50km/h or even at 80 km/h. I have owned a couple of these E320's and on this car nothing happens when you switch from D>4. Also the S-E switch definitley is not working. Appreciate any help with this.

 

[colinspain]

What happens when you use the D <> 4 switch above 50 mph?

Nick Froome
the independent Mercedes Estate specialists

Thank you but there is no change above 50km/h or even at 80 km/h.

 

[bolide]

Thank you but there is no change above 50km/h or even at 80 km/h.

So it never makes it into 4th, even when the lever is moved to the left?

Nick Froome
the independent Mercedes Estate specialists

 

[colinspain]

So it never makes it into 4th, even when the lever is moved to the left?

Nick Froome
the independent Mercedes Estate specialists

Thats right it stays in 5th when I move the lever across to 4 even at high speed. Gear changes are ok from start: 2nd -3rd - 4th then unless I keep the throttle fairly hard down it goes immediately into 5th. Like into 4th then 5th in a split second. It may have something to do with the E -S switch not working. The only way I can keep it in 4th and then only for a very short time is to accelerate hard through the gears. It is also very slow to drop down a gear when I accelerate to overtake whilst in 5th but if I kick it down into the floor it seems to drop down 2 gears quickly. Appreciate your time. Thnx
Colin

 

[ray_hennig]

I had that ...

Thats right it stays in 5th when I move the lever across to 4 even at high speed. Gear changes are ok from start: 2nd -3rd - 4th then unless I keep the throttle fairly hard down it goes immediately into 5th. Like into 4th then 5th in a split second. It may have something to do with the E -S switch not working. The only way I can keep it in 4th and then only for a very short time is to accelerate hard through the gears. It is also very slow to drop down a gear when I accelerate to overtake whilst in 5th but if I kick it down into the floor it seems to drop down 2 gears quickly. Appreciate your time. Thnx
Colin

Yours is more recent than mine but I think we both have the 722.5 box. This box has some rudimentary electronic control on 4th/5th. I also had the slow change-down you refer to. It was almost as if the box went into some sort of 'safe' mode and things were pretty disappointing, just as you describe.

I built an LED code reader and read error codes associated with the box. I erased the codes and, voila, back to normal again and things have been fine for quite a while now. The symptoms started after engine mounts were changed but I have no idea why.

As I say, yours is more recent and has, I think, different codes and, possibly, means of reading them. There are others here who commented on my efforts and my success and this might jog their memories and they may return with advice specific to your wheels.

Bonne chance.

RayH

 

[WDB124066]

I have heard of this before and read something on here (I think) about the fix about two years ago IIRC. From memory it was a reasonably easy fix and something electronic?? but I really can’t recall precisely, the search feature may help........??

 

[ray_hennig]

I have heard of this before and read something on here (I think) about the fix about two years ago IIRC. From memory it was a reasonably easy fix and something electronic?? but I really can’t recall precisely, the search feature may help........??

Try here:

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1529415-gearshift-problem-722-5-a.html

and here:

Gearshift problem on 722.5 (5.speed) - Mercedes-Benz Owners' Forums

and here:

Gearshift problem on 722.5 - Page 3 - Benzworld.org - Mercedes-Benz Discussion Forum

May help.

RayH

 

[WDB124066]

INTERMITTENT NO 5TH GEAR​

Check loose connections at throttle valve switch. Check for
poor or loose wiring connections between TCM and transmission. See
WIRING DIAGRAMS. Ensure proper TCM is installed.​

NO 5TH GEAR OR TRANSMISSION SHIFTS TO 5TH UNDER LOAD​

Check and repair vacuum line between intake manifold and​

ignition control unit.

 

[bolide]

The 5th gear system uses a complex combination of signals to govern the system. There is a PDF available on this

General
The electronics control the engaging and
disengaging of 5th gear.

The 5-speed automatic transmission control unit (N15/1) receives the following electrical information:
* voltage supply
* engine speed
* load signal
* accelerator pedal switch
* vehicle speed signal
* D contact switch
* kickdown switch
* E/S mode selector switch
* control valve
• diagnosis

From memory the system for the early CIS cars is different to that for the late HFM cars and the details are above are for an early car

I had one late car which would not engage 5th and which seemed not to know what gear it was in. It would stutter leaving roundabouts because a period of freewheeling would leave it confused. The fault was a loose pin on the OVP socket which feeds speed signal into the system via the OVP. No speed signal - gearbox doesn't know what to do

So I'd look for simple faults first around the feeds to the control relay

Nick Froome
the independent Mercedes Estate specialists

 

[colinspain]

The 5th gear system uses a complex combination of signals to govern the system. There is a PDF available on this

General
The electronics control the engaging and
disengaging of 5th gear.

The 5-speed automatic transmission control unit (N15/1) receives the following electrical information:
* voltage supply
* engine speed
* load signal
* accelerator pedal switch
* vehicle speed signal
* D contact switch
* kickdown switch
* E/S mode selector switch
* control valve
• diagnosis

From memory the system for the early CIS cars is different to that for the late HFM cars and the details are above are for an early car

I had one late car which would not engage 5th and which seemed not to know what gear it was in. It would stutter leaving roundabouts because a period of freewheeling would leave it confused. The fault was a loose pin on the OVP socket which feeds speed signal into the system via the OVP. No speed signal - gearbox doesn't know what to do

So I'd look for simple faults first around the feeds to the control relay

Nick Froome
the independent Mercedes Estate specialists

Hello All,
Just want to thank eveyone for this great response and will do through all the suggestions and hopefully sort this problem. Many thanks everyone and will let you know if I have success.
Colin

 

[colinspain]

Try here:

Gearshift problem on 722.5 - Benzworld.org - Mercedes-Benz Discussion Forum

and here:

Gearshift problem on 722.5 (5.speed) - Mercedes-Benz Owners' Forums

and here:

Gearshift problem on 722.5 - Page 3 - Benzworld.org - Mercedes-Benz Discussion Forum

May help.

RayH

Hi Ray I am making a LED blink tester as per the Link on your answer. It's fairly simple to make and easy to connect but which number on the 16 pin multi socket would I use to plug into with the third plug (yellow on the diagram) to clear the auto box error codes. I am fairly sure this is the problem as many other members have cured this problem by the same method. The nearest Merc dealer here in Spain is not insterested in these older models and say they do not have the cables anyway. Do you know where the TCM N15/1 transmission control module is fitted on my car. W124 E320 Cabrio 5spd Auto 1994
Many thanks for your assistance. Colin

 

[bolide]

To locate the module I'd look in the ECU rack behind the battery first. It'll probably look like a big relay

If it's not there it might be in the relay box behind the fusebox (though I doubt it) or under the footplate in the passenger footwell

Nick Froome
the independent Mercedes Estate specialists

 

[ray_hennig]

Bit difficult to help as I'm now in Paris ...

Hi Ray I am making a LED blink tester as per the Link on your answer. It's fairly simple to make and easy to connect but which number on the 16 pin multi socket would I use to plug into with the third plug (yellow on the diagram) to clear the auto box error codes. I am fairly sure this is the problem as many other members have cured this problem by the same method. The nearest Merc dealer here in Spain is not insterested in these older models and say they do not have the cables anyway. Do you know where the TCM N15/1 transmission control module is fitted on my car. W124 E320 Cabrio 5spd Auto 1994
Many thanks for your assistance. Colin

The connector block on mine is on the battery side, in front of the battery. It's got a plastic cover over it and it's sort of oblong with 4mm female connectors. I think the block will host up to 166 connections but not all on mine are populated.

Keep searching in the other links because I recall posting a description of the block. Sorry I can't help more; I'm working in Paris and all my stuff is miles away.

Do remember that yours is more recent.

Good hunting.

RayH

 

[colinspain]

To locate the module I'd look in the ECU rack behind the battery first. It'll probably look like a big relay

If it's not there it might be in the relay box behind the fusebox (though I doubt it) or under the footplate in the passenger footwell

Nick Froome
the independent Mercedes Estate specialists

Thanks again Nick any ideas on the correct socket in the 16 pin multi socket I use to clear the gearbox error codes. The diagram doesn't mention which one to use for the auto box. 1 and 16 which are the 12v supply and some of the sockets are not used.
Colin

 

[colinspain]

The connector block on mine is on the battery side, in front of the battery. It's got a plastic cover over it and it's sort of oblong with 4mm female connectors. I think the block will host up to 166 connections but not all on mine are populated.

Keep searching in the other links because I recall posting a description of the block. Sorry I can't help more; I'm working in Paris and all my stuff is miles away.

Do remember that yours is more recent.

Good hunting.

RayH

Enjoy Paris and many thanks for your help. I'll keep trying as have made the code reader now.
Colin

 

[ray_hennig]

Drunk again ...

Enjoy Paris and many thanks for your help. I'll keep trying as have made the code reader now.
Colin

166 connectors, I don't think so. Sorry, I meant 16!

You've probably seen through me!.

RayH

 

[lakhbir singh]

look at the voltage supply.. it may work