W208 CLK55 AMG Passenger Power Seat Not Working

[Kaleb Bailey]

Hello all,

I purchased a (W208) 2001 CLK55 AMG a little over a year ago. It had a multitude of problems that I have fixed and addressed (with plenty of raging moments). As of recent, I've decided to try to fix the power seat issue with the passenger side (*Driver side has full functionality*). The seat has not worked since the car was originally purchased. What I've done/covered so far:

I have taken the seat out, inspected wires and cleaned tracks to ensure nothing was broken or impeding movement. I have checked the motors by applying power directly to them and they checked out. I tested the door switch by measuring voltage changes to the seat module when the switches on the door are pressed (voltage does change). I have checked the fuses a multitude of times and will do so again.

As of right now, I've found a corroded ground wire (will be cleaning that) under the carpet as well as another little box with a small yellow connector plugging into it. There are some other wires down there as well that I have yet to check. What relation does that stuff under the carpet have to the seat's functionality? Any ideas on what to do?

I'm hesitant to take it to a Mercedes dealer to have the seat inspected / fixed due to expense. How much would they charge for just a code read? My current project goals with this car do not allow for expensive dealer prices. Any help is appreciated, thanks

 

[bembo449]

this has got to be a wiring problem , I think I would bite the bullet and strip that side out so you can apply 12v further and further back in the harness to the point where you no longer get and movement in the seat , I don't know if its possible for "star" to diagnose such a problem but if it was , use a reputable INDY recommended on here and NOT an MB dealer

 

[bigasotonuk]

Hi,
Bit confused by the way you worded it but are you saying both front seats are at fault or just the driver's seat? Does the car have the memory function?
What I have written below is applicable if its a single inoperative seat with memory function.
Regular switching operation testing is almost certainly not applicable as the seats are controlled on the CAN Bus
I believe the seat switches are plugged directly into the Door Control Module (DCM), the box under the seat is the seat control module which feeds the motors.
Both the Seat control module and the DCM are on the CAN Bus, so are only connected with a twisted pair signal cable
Common issue with these cars is a failing DCM, additionally it is not unknown to find the pins/plugs partially dislodged pulled out of the connectors, possibly due to things getting jammed under seat.
Has it been plugged into STAR? as these units are on the CAN they will throw up codes and there are various activation and tests can can be carried out to isolate the issue.
I would definitely NOT be taking it to MB where in the UK are you? I am sure someone will be able to recommend a Mercedes specialist near you.

 

[bigasotonuk]

Hello all,

I purchased a (W208) 2001 CLK55 AMG a little over a year ago. It had a multitude of problems that I have fixed and addressed (with plenty of raging moments). As of recent, I've decided to try to fix the power seat issue with the passenger side (*Driver side has full functionality*). The seat has not worked since the car was originally purchased. What I've done/covered so far:

I have taken the seat out, inspected wires and cleaned tracks to ensure nothing was broken or impeding movement. I have checked the motors by applying power directly to them and they checked out. I tested the door switch by measuring voltage changes to the seat module when the switches on the door are pressed (voltage does change). I have checked the fuses a multitude of times and will do so again.

As of right now, I've found a corroded ground wire (will be cleaning that) under the carpet as well as another little box with a small yellow connector plugging into it. There are some other wires down there as well that I have yet to check. What relation does that stuff under the carpet have to the seat's functionality? Any ideas on what to do?

I'm hesitant to take it to a Mercedes dealer to have the seat inspected / fixed due to expense. How much would they charge for just a code read? My current project goals with this car do not allow for expensive dealer prices. Any help is appreciated, thanks

Apologies just re-read youre post and the thread title, please ignore my first paragraph of my post.

 

[mattkh]

Apologies just re-read youre post and the thread title, please ignore my first paragraph of my post.

Thanks for the post. You sound like an expert on CAN bus. Please elaborate on a CAN bus. How many CAN buses would there be on one car. Who controls the CAN bus? Is the signal on a CAN bus just to activate a slave module OR is the signal there all the time?
Thanks in advance.

 

[Kaleb Bailey]

this has got to be a wiring problem , I think I would bite the bullet and strip that side out so you can apply 12v further and further back in the harness to the point where you no longer get and movement in the seat , I don't know if its possible for "star" to diagnose such a problem but if it was , use a reputable INDY recommended on here and NOT an MB dealer

Okay, I'll do so tomorrow and update if I have any luck. I appreciate your help

 

[Kaleb Bailey]

Hi,
Bit confused by the way you worded it but are you saying both front seats are at fault or just the driver's seat? Does the car have the memory function?
What I have written below is applicable if its a single inoperative seat with memory function.
Regular switching operation testing is almost certainly not applicable as the seats are controlled on the CAN Bus
I believe the seat switches are plugged directly into the Door Control Module (DCM), the box under the seat is the seat control module which feeds the motors.
Both the Seat control module and the DCM are on the CAN Bus, so are only connected with a twisted pair signal cable
Common issue with these cars is a failing DCM, additionally it is not unknown to find the pins/plugs partially dislodged pulled out of the connectors, possibly due to things getting jammed under seat.
Has it been plugged into STAR? as these units are on the CAN they will throw up codes and there are various activation and tests can can be carried out to isolate the issue.
I would definitely NOT be taking it to MB where in the UK are you? I am sure someone will be able to recommend a Mercedes specialist near you.

I believe I tested the DCM as working (thats what I was referring to when talking about the "switches" unless I'm still thinking incorrectly.) It is the little panel with the seat and 3 presets and 1 memory button correct? Anywho, it has NOT been plugged into STAR, I'm not sure of anyone around me that is reputable/has the right tool. I'm actually in the US but no one on U.S forums have seemed to be helpful and this car seems to be nonexistent over here lol

I will check the connectors for pulled pins and possibly reflow some of them. If I have no luck with bembo's advice, I will certainly consider finding someone with STAR. Thank you for your help

 

[bigasotonuk]

Hi
I am not sure you have identified the DCM correctly it is actually fitted to the door itself and if I am correct, you door card mounted seat switches are plugged into it.
Have a look at the ebay auction below purely so you can identify it
https://www.ebay.co.uk/itm/Mercedes...940079&hash=item3dae22394e:g:U1YAAOSwisRfmAFd

 

[Kaleb Bailey]

Hi
I am not sure you have identified the DCM correctly it is actually fitted to the door itself and if I am correct, you door card mounted seat switches are plugged into it.
Have a look at the ebay auction below purely so you can identify it
https://www.ebay.co.uk/itm/Mercedes...940079&hash=item3dae22394e:g:U1YAAOSwisRfmAFd

Ah okay, that makes a lot more sense. After shaking the seat control module (the one under the seat) it sounds like one of the relays has a loose part in it so I'm assuming that may be the issue. I'm ordering a new one and will hope that works. If not, I'll give the DCM a look. Thanks!

 

[bigasotonuk]

Hi
Just put the Pt.No. of the control unit into ebay, get a second hand one its likely to be pretty expensive new.
Hope it sorts it for you.

 

[Kaleb Bailey]

Hi
Just put the Pt.No. of the control unit into ebay, get a second hand one its likely to be pretty expensive new.
Hope it sorts it for you.

Hello again! I received the new (used) unit yesterday and got around to installing it today. The seat finally works! I appreciate your help. The best of luck to you in the future

 

[bigasotonuk]

Hi,
Glad you have got it sorted, thanks for posting back.
Stay Safe

 

[bembo449]

Great result and persistence pal

 

[mattkh]

Very happy for you.
If you open up the seat control module to see what was rattling inside it, please put up a picture. Thanks

 

[Kaleb Bailey]

Very happy for you.
If you open up the seat control module to see what was rattling inside it, please put up a picture. Thanks

Hey Matt,
I already had the SCM opened to check for burnt legs on any SMTs on the board, and there were no visually loose parts. When I would shake it, it would sound like a spring was out of place in one of the black relays (I believe there are 4 off the top of my head). I received my new unit that has this similar noise, but it doesn't seem as loud so maybe they were designed a little loose? I'm not sure. I will try to upload a pic and circle what I'm referencing if you would still like me to

 

[mattkh]

Thanks. No need for the photo now that you have reminded me about springs inside the relays.