Automatic trunk closer retrofit on w205
Now, after spending quite alot of time and money to actually get all the parts from different persons on ebay ,mind you that alot of money were lost on behalf of
people not wanting to sell me specific parts (no one had all the parts).
So to the issue at hand, I am not able to locate a wiring loom as I initially thought would be available, so this makes this install very not so plug n' play...ish.
No worries, I sought ought to find a mercedes service manual... so the install could be once again finished by myself but the problem is after finding the said manual
again I found myself in despair as it was a bit difficult to understand, mainly the wiring diagrams and also what connects to what and where ...
After explaining my whole situation I ask the forum if anyone has attempted to retrofit an automatic trunk closer feature?If not I will continue to advance on my own, will be posting photos soon as I proceed

Remote trunk closing works perfectly.
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Trim panel- A2056908904 (not really needed, you can just cut a hole in your own trim panel for the switch).
Control unit- A2229006008 (has to be brand new from MB as they are VIN locked)
Motor- A2058200042 (this also needs some other little parts to attach to the trunk arm, but my used one came attached to the trunk arm!)
Striker plate- A2057600700
Actuator- A2047500060 (also needs a cable to attach it to the striker plate- again, I got the striker plate and actuator from a used vehicle which included the wire)
Actuator insulation- A2057500060 (this is a plastic box and foam to attach the actuator to the mounting point in the trunk)
Release switch (cabin)- A2229052303
Boot release switch- A2208217251 (different switch is needed if you have keyless entry)
Bracket- A2055452240 (to mount the control unit to the trunk)
Console- A2057500031 (to mount the motor to the trunk)
Nut- N910112006001 - 10mm M6x 1.0mm (to mount the console)
Bolt- A0119908804 - M5x 20 (also to mount the console)
Stanchion-A2057570082 (a small plastic link arm to attach the bottom of the motor onto the trunk. Also needs some grommets at either end).
The whole thing does need coding. I had this done by COMAND.co.uk near Guildford. They were fantastic and really helpful. They can get a wiring loom made up for people too, but it’s probably cheaper to get all the wiring from a car that’s being dismantled.
I’ll add the wiring diagrams etc when I get a chance.
Trim panel- A2056908904 (not really needed, you can just cut a hole in your own trim panel for the switch).
Control unit- A2229006008 (has to be brand new from MB as they are VIN locked)
Motor- A2058200042 (this also needs some other little parts to attach to the trunk arm, but my used one came attached to the trunk arm!)
Striker plate- A2057600700
Actuator- A2047500060 (also needs a cable to attach it to the striker plate- again, I got the striker plate and actuator from a used vehicle which included the wire)
Actuator insulation- A2057500060 (this is a plastic box and foam to attach the actuator to the mounting point in the trunk)
Release switch (cabin)- A2229052303
Boot release switch- A2208217251 (different switch is needed if you have keyless entry)
Bracket- A2055452240 (to mount the control unit to the trunk)
Console- A2057500031 (to mount the motor to the trunk)
Nut- N910112006001 - 10mm M6x 1.0mm (to mount the console)
Bolt- A0119908804 - M5x 20 (also to mount the console)
Stanchion-A2057570082 (a small plastic link arm to attach the bottom of the motor onto the trunk. Also needs some grommets at either end).
The whole thing does need coding. I had this done by COMAND.co.uk near Guildford. They were fantastic and really helpful. They can get a wiring loom made up for people too, but it’s probably cheaper to get all the wiring from a car that’s being dismantled.
I’ll add the wiring diagrams etc when I get a chance.
In my 2016 C450 I have to add/modify wiring for the following components:
S62/26 trunk mounted closing switch
N121 trunk closing control unit
H4/60 warning buzzer
M51 trunk opening/closing motor
M14/31 striker plate motor
N38 rear switching module
I also have to add the following fuses into the K40/5 rear fuse and relay box along with wiring:
F458 / 5a - N38 rear switching module
F464 / 40a and F413 / 5a - N121 trunk closing/opening module
The actual component installation isn't bad, just the wiring that's a bit of an ordeal.
Some/most of the wiring is none existent. And to get it, you either have to know exactly what your looking for and remove/cut it out of a parts vehicle, or custom make it.
You have to add the N121 control unit into CAN B as well.
The correct way is to run a twisted pair from the N121 control unit to the X30/32 CAN B potential distributor block at the driver side front seat, but I just spliced into the N69/5 Keyless go module CAN B wiring.
Then the vehicle has to be coded for it to work. Either by a dealership that is willing to do retrofit coding, or an aftermarket Benz shop.
TBH It's a bit of a PIA, but worth it for $600ish worth of parts, $130 dealership visit, and a couple days labor.
In my 2016 C450 I have to add/modify wiring for the following components:
S62/26 trunk mounted closing switch
N121 trunk closing control unit
H4/60 warning buzzer
M51 trunk opening/closing motor
M14/31 striker plate motor
N38 rear switching module
I also have to add the following fuses into the K40/5 rear fuse and relay box along with wiring:
F458 / 5a - N38 rear switching module
F464 / 40a and F413 / 5a - N121 trunk closing/opening module
Some/most of the wiring is none existent. And to get it, you either have to know exactly what your looking for and remove/cut it out of a parts vehicle, or custom make it.
You have to add the N121 control unit into CAN B as well.
The correct way is to run a twisted pair from the N121 control unit to the X30/32 CAN B potential distributor block at the driver side front seat, but I just spliced into the N69/5 Keyless go module CAN B wiring.
Then the vehicle has to be coded for it to work. Either by a dealership that is willing to do retrofit coding, or an aftermarket Benz shop.
TBH It's a bit of a PIA, but worth it for $600ish worth of parts, $130 dealership visit, and a couple days labor.

In my 2016 C450 I have to add/modify wiring for the following components:
S62/26 trunk mounted closing switch
N121 trunk closing control unit
H4/60 warning buzzer
M51 trunk opening/closing motor
M14/31 striker plate motor
N38 rear switching module
I also have to add the following fuses into the K40/5 rear fuse and relay box along with wiring:
F458 / 5a - N38 rear switching module
F464 / 40a and F413 / 5a - N121 trunk closing/opening module
The actual component installation isn't bad, just the wiring that's a bit of an ordeal.
Some/most of the wiring is none existent. And to get it, you either have to know exactly what your looking for and remove/cut it out of a parts vehicle, or custom make it.
You have to add the N121 control unit into CAN B as well.
The correct way is to run a twisted pair from the N121 control unit to the X30/32 CAN B potential distributor block at the driver side front seat, but I just spliced into the N69/5 Keyless go module CAN B wiring.
Then the vehicle has to be coded for it to work. Either by a dealership that is willing to do retrofit coding, or an aftermarket Benz shop.
TBH It's a bit of a PIA, but worth it for $600ish worth of parts, $130 dealership visit, and a couple days labor.
Thanks in advance
Last edited by Mastersean; Jul 8, 2022 at 05:00 AM.
In my 2016 C450 I have to add/modify wiring for the following components:
S62/26 trunk mounted closing switch
N121 trunk closing control unit
H4/60 warning buzzer
M51 trunk opening/closing motor
M14/31 striker plate motor
N38 rear switching module
I also have to add the following fuses into the K40/5 rear fuse and relay box along with wiring:
F458 / 5a - N38 rear switching module
F464 / 40a and F413 / 5a - N121 trunk closing/opening module
The actual component installation isn't bad, just the wiring that's a bit of an ordeal.
Some/most of the wiring is none existent. And to get it, you either have to know exactly what your looking for and remove/cut it out of a parts vehicle, or custom make it.
You have to add the N121 control unit into CAN B as well.
The correct way is to run a twisted pair from the N121 control unit to the X30/32 CAN B potential distributor block at the driver side front seat, but I just spliced into the N69/5 Keyless go module CAN B wiring.
Then the vehicle has to be coded for it to work. Either by a dealership that is willing to do retrofit coding, or an aftermarket Benz shop.
TBH It's a bit of a PIA, but worth it for $600ish worth of parts, $130 dealership visit, and a couple days labor.









