W203 - Memory seats retrofit

[KevinH2000]

I've been studying the information and components I have acquired to this point and this is my present thinking.

The wiring under the seat is significantly different in the non-memory seat cars. This is a picture of the non-memory component of the wiring connections under the seat of the donor car:

The yellow connector is for the air bag system. I need to determine the purpose of the blue connector.

This photo shows the under-seat connections of Jake's car (Jake is a fellow W203 owner I met through the MBWorld forum) which has the memory function:

Note that one of the connection points is unused

This is a photo of the wiring currently under my seat.

I should not have to touch the air bag (yellow connector) and I will need to switch the black connector at the left to the memory module in order to provide power. Note that I had to graft the connector for the C63 (W204) seat power onto my wiring harness, but the W203 connector still has power. I can remove the W204 connector after I'm sure I can make the memory work.

This is a photo of the seat control module with the wiring I removed from the donor car.

Note the information under the bar code:

It appears that the CAN Bus connection is in the large black connector.

In order to connect the memory function to the seat I will need to find a wiring diagram for the seat module and:

1. Determine which wires in the large black connector are CAN High and CAN low.
2. Determine what the blue connector does and if needed how to connect it to my seat.
3. Whether I need to connect any of the other wires. They may send messages to the steering wheel and mirrors. If that is the case, I may not need to connect them.

There is a CAN block under the dash on the driver's side that I can use to connect the CAN wiring.

I may return to the donor car to harvest part of this.

I will also need to activate the system using DAS. Fortunately, Jake and I have joint custody of a system and I've seen the menu showing the activation screen.

Here's the system in my car which currently does not memory seats operational:

Note that the Driver Memory Seat Function is set to "Not Present."

Here's the reading from Jake's Car showing the Driver Memory is Present.

Again - Any insights on the wiring will be welcome. I think I am getting close to understanding how this works, but I still have a gap in my knowledge.

 

[andy27168]

Hi,
Unlike the earlier chassis's I believe there is no wiring between the door switches and the seats.
My understanding is that the functions of the switches are wired to the door control unit.
As the DCM and the seat control unit are on the CAN BUS the switch functions utilize this.
A 203 chassis may also need the cluster coding and if fitted almost certainly the central gateway as well.

 

[Hectors Dad]

I've been studying the information and components I have acquired to this point and this is my present thinking.

The wiring under the seat is significantly different in the non-memory seat cars. This is a picture of the non-memory component of the wiring connections under the seat of the donor car:

The yellow connector is for the air bag system. I need to determine the purpose of the blue connector.

This photo shows the under-seat connections of Jake's car (Jake is a fellow W203 owner I met through the MBWorld forum) which has the memory function:

Note that one of the connection points is unused

This is a photo of the wiring currently under my seat.

I should not have to touch the air bag (yellow connector) and I will need to switch the black connector at the left to the memory module in order to provide power. Note that I had to graft the connector for the C63 (W204) seat power onto my wiring harness, but the W203 connector still has power. I can remove the W204 connector after I'm sure I can make the memory work.

This is a photo of the seat control module with the wiring I removed from the donor car.

Note the information under the bar code:

It appears that the CAN Bus connection is in the large black connector.

In order to connect the memory function to the seat I will need to find a wiring diagram for the seat module and:

1. Determine which wires in the large black connector are CAN High and CAN low.
2. Determine what the blue connector does and if needed how to connect it to my seat.
3. Whether I need to connect any of the other wires. They may send messages to the steering wheel and mirrors. If that is the case, I may not need to connect them.

There is a CAN block under the dash on the driver's side that I can use to connect the CAN wiring.

I may return to the donor car to harvest part of this.

I will also need to activate the system using DAS. Fortunately, Jake and I have joint custody of a system and I've seen the menu showing the activation screen.

Here's the system in my car which currently does not memory seats operational:

Note that the Driver Memory Seat Function is set to "Not Present."

Here's the reading from Jake's Car showing the Driver Memory is Present.

Again - Any insights on the wiring will be welcome. I think I am getting close to understanding how this works, but I still have a gap in my knowledge.

Going from my S212 retrofit all of the memory functions for the motors are contained and carried out by the Seat Control Module. All you need connected (if you are not doing the steering column and mirrors) are airbag connector (normally yellow), seat heating (probably the Brown / Black & Green), occupancy sensor (possibly the blue plug but that's a guess) and the main connector (15 pin I think from memory).

Everything apart from the main 15 pin connector should be a straight swap. The 15 pin connector only needs CAN H, CAN L, Positive, Negative to work. All of the other wires are for steering column motors, Hall sensors and mirrors. You will then need to code your car to see the new Seat Control Module and it's memory function.

CAN cables for the Merc seats are normally brown / brown & red and look like twisted pair cables normally found in CAT network cabling (they are in fact FLRY automotive cable). The positive will be the 4.0mm red/yellow (probably red/white on the other side).

On the S212 power is fed to the front seats from the rear SAM (pins 44 & 45 from memory but do check) and they had to be moved to new positions (62 & 65 I think). This is because the normal seats lose power as soon as you switch off the ignition whereas the memory seats get power as soon as either front doors is opened (you can then press the memory button and move the seat before you get in).
If you don't move the power it also causes a parasitic drain that will flatten your battery.

Good luck!

 

[KevinH2000]

I finished my memory seat retrofit on the driver’s side (U.S vehicle).). You can read the details here. My write up is not a step-by-step DIY guide. It does show the process I went through to sort this out.

I think there is some further improvement possible but this will require the use of the Star diagnostic equipment. Unfortunately, I am having difficulty with my “cloned” Star system and when I have that issue resolved I will provide a further update. I am in the process of acquiring parts for the passenger side. I will provide an update on that work too.


I was surprised to learn that the car’s central nervous system recognized the seat module when I attached it to the CAN node. I spent a lot of time trying to program the system with DAS which turned out to be unnecessary.

I did not attempt to activate the mirror or steering wheel motor which was part of the factory system.

 

[Hectors Dad]

I finished my memory seat retrofit on the driver’s side (U.S vehicle).). You can read the details here. My write up is not a step-by-step DIY guide. It does show the process I went through to sort this out.

I think there is some further improvement possible but this will require the use of the Star diagnostic equipment. Unfortunately, I am having difficulty with my “cloned” Star system and when I have that issue resolved I will provide a further update. I am in the process of acquiring parts for the passenger side. I will provide an update on that work too.


I was surprised to learn that the car’s central nervous system recognized the seat module when I attached it to the CAN node. I spent a lot of time trying to program the system with DAS which turned out to be unnecessary.

I did not attempt to activate the mirror or steering wheel motor which was part of the factory system.

Yeah, you're welcome.

Used my insight and experience verbatum on another forum and didn't even acknowledge the source - THANKS!

 

[KevinH2000]

I regret that I didn’t provide more specific credit for your assistance and I hope that you will not hold my error against me. I did provide a link to this thread in the third post of the information I placed on the other boards. In retrospect I should have given more credit and a sincere thank you for the insight you provided. I don’t want to make excuses but I normally post updates late at night and my thought processes are not at their peak efficiency. I will take steps to clarify your contributions on the other boards.
Thanks