AbuBakar88

I just bought a used 2008 w221 s550 (it’s very clean and less than 80k miles) and it had some minor electrical issues but I was able to solve them easily (most issues were blown fuses). But the one that I can’t solve is the electric seat adjustment for the front passenger. The lock/unlock function works fine but no heated or ventilated seats and the seats adjustment don’t work. I read somewhere that a software update can solve most cosmetic issues with the 221.

can anyone confirm to me that a software update will solve seat adjustment issue or do I just need to change the entire module??

BOTUS

software won't sort the seat

take a look at the underneath at the front and see if the module is plugged in

AbuBakar88

I have examined the door module itself, the window controls work fine and the lock/unlock works fine too. But the seats still don’t respond

BOTUS

on old cars the motors and cables that drive the seats can break - but its not something I've heard happen on the 221 - but it must happen sometime

unlikely the door module... although if very high miles the door loom may have worn out

there's a module in the back of the seat for massage if fitted - they play up all the time as the hoses split and if you leave long enough the pump to makes the air gives up in the boot
underneath the seat is the module that does the memory and the air bag weight sensor if fitted

WRC-LVR

Botus is referring to the seat module under the seat. NOT the door module(s).

AbuBakar88

is the module underneath the seat or inside the back of the seat??

BOTUS

on the floor at the front of the seat

AbuBakar88

I diagnosed the seat controls on a computer and the system reads the commands but the seat does not physically move. I have checked all the wires and they all seam to be fine with voltage running through them and the module all seem alright. I’m beginning to think the seat motors have blown out but I feel it’s highly unlikely that all 3 are bad at the same time.

I saw an error message that says there’s under voltage in the ECU, could that be why the seats aren’t working and how do I solve it??

BOTUS

I don't think it will be this - but may affect other stuff...

a 2008 model might have a small 35 amp/hr battery under the bonnet (more like one for a baby car 30 years ago) - if so in the boot hidden will be a massive one that is often never touched - at this age if still original it will be worn out and would be worth replacing

these car each amps for fun and even a new battery won't keep the car alive for more than 25 mins without the engine running - of course the more toys the more it eats...

if it has the rear battery and its the original it won't help the car behave correctly - they throw errors for fun if the volts are in anyway low