Photo DIY - SRS Seat Sensor replacement

Update to this saga. I took the disassembled seat to an auto trim shop here in Cookeville Monday, and for the $51 he completely disassembled the seat, put the sensor pad in correctly and reassembled the seat. He did not however reinstall the seat. Which Im trying to do now...
Im trying to get the connectors in correctly, I'll describe the female side first, the male side connects to the seat. I have the yellow connector, which drives the SRS, a Red connector which has 4 female pins, of which only two are used, and a black connector which only has two male pins....Heres the rub. The black connector pins came out, and are now dangling loose. They are a purple wire and a brown wire.
The female side has a solid brown wire and a brown/white stripe wire that come in. The purple/brown combo are vertical. Can anyone tell me which male pin (purple or solid brown) connects to which female (solid brown/brown/white stripe?)
Ive tried both ways. Every function on the seat works fine except two.
1) The headrest relay works fine, I can hear it click, but the headrest will not go up/down on the seat.
2) The SRS light on the dashboard is still on, but the Airbag on/off light on the passengers side of the console now goes off when the vehicle is started, which previously it was lit fulltime.
Questions oh great internet guru-types.
1) Purple/Brown placement, can someone look on a working car and tell me how it goes?
The drivers side doesnt seem to use the same color wires I think, Im going to go disassemble it, but thought Id ask here too. The drivers side uses three wires in the black connector, unlike the passenger side which uses two.
2) Does this SRS thing now work, since the airbag light is off, even thought the dashboard light is still on?

Put another one in the WIN column.

After running out of time and patience a couple of months ago, I finally had access to the car, nice weather and enough time to actually TAKE my time.

The seat came out easily, since I was familiar with that process from the first go around. I had the necessary torx heads bits to loosen the frame from the seat this time. I removed the entire seat pad by pulling the bar out of the back as well.

Twisting the white plastic clips popped the cover loose. The sensor slid right out after I removed the insert that covers the white control box and pulled the wire through the hole in the cushion.

The hardest part was getting the white clips to bite back into the wire that holds the cover on. I used a spark plug socket underneath and was able to press the wire into the clips.

The only way to get the yellow socket out that I could see was to remove the plastic plug panel from the frame via the two screws on either side. Then I popped the back off and the yellow socket slid right out.

I wish I had read posts from sjphill before I started. I would have paid attention to the wires. I was working from memory, though. Sorry.

All the rest was as described.

Thanks for the instructions. The SRS light is out.

On to the brake light switch next.

I swaps the front cushions few days ago and while pulling the sensor, I broke it. I was not impreesed with that. MB quoted me 90 pounds for a new one...
I fixed it, now, I don't know how long it will hold but its working.
The sensor coil was broke in half. I tried to put it back together but there was no way possible. It was not working.
After many attempts like scrapping the plastic with a razor blade to uncover the conductor, it just shreed away as too thin.
I was able to separate the two plastic half enclosing the conductor but bugger, the one side that was free was the black one, the protective non conductive part...
At this time, I decide to put some acetone on the back black stuff ant it disolved it, revealing the meatalic conductor. This took a lot of time and thinking but finally I got it.
From there I just taped some wire to the conductor. Its not pretty but it work. You need to understand that I went so many times back and forth that at the end, pretty or not pretty, who cares.
The main thing, it work, dunno for how long though.
Olivier

Hey Guys,

I really appreciate this thread:
As I have the same prob.
ONly I am going to spring for the 700 beans to my mechanic
two reasons:
1. its complicated and time consuming, I can handle one or the other but not both at once.
2. i drive like a maniac and my wife sits in the passenger seat. i dont want to hear it for the rest of my life: "so you didnt fix it yata yata and we crashed yata yata"
you marrieds know the drill.

much obliged,

Max

Seat sensor Pad replacement 2001 E55

I replaced my sensor pad today and this thread was most helpful. My car has a pneumatic seat and this was not really addressed. I could not easily remove the air tubing and was afraid to force the angled connector from its attachment at the seat. I made a small cut in the tubing and slid it off leaving the connecto in place. The control box for the pneumatic seat is rivetted to the frame. Rather than drill out the rivets, I bent it out enough to access the seat cover attachement, When I elevated the leather, there were more layers of material than shown in this post in order to encase the air bladder in the seat bottom. I wound up unhooking the seat cover from the clips and sliding the old sensor out from between the padding and the cover. It would not fold back all the way as shown in the photos posted here. I was able to slide it in between & re-hook the cover. Re-assembled in reverse order. The next problem was hooking back up the air tube to the angled gray connector. It would not "slide" back on. I tried to heat it with a flame and got it to go baack on partially. It Leaked. I wound up using a hemostat (small surgical clamp) inside the opening of the tube and spread while applying a flame from a lighter. This softened the tubing and allowed it to open enough to immedialtly slide it back over the connector where it contracted and sealed (thank goodness). There may be a better way. If somone knows for sure how to disconnect the tubing it might help the next guy with avoiding the headache and possible leak. I was more afraid of damaging the connector and really being stuck. The SRS light is off and no leaks. I hope this helps some others to avoid the $700 the Stealership wanted.

STOP... DO NOT FOLLOW THESE PROCEDURES (yet). DO NOT BUY A NEW SENSOR YET.

THE SOLUTION MAY BE A LOT SIMPLER, as already indicated by a previous poster.

MB are great cars mechanically, but electrically they are behind a bit. (not sure if they lack incentives to improve).

As indicated before a few times on this thread, one of the 3 sensor wires between the connector and the sensor box under the seat cushion can break. I had the same problem. Unfortunately I had already bought the new sensor (as the dealer told me it had failed and that it was very common. SURE).

So what most likely is going on is the following:
1. Each wire has only one thick thick and brittle strand of copper.
2. The way the tie wraps are placed under the seat to hold the cables together it seems that stress is placed on the wires as the seat is moved up and down and you know what happens on cheap single strand wires when you flex them back and forth a bit. It only takes one and only one strand crack for the circuit to open.

In my case the white wire lost continuity between the yellow connector and just as it went into the hole under the seat. Most likely the crack would occur near the place where the tie wrap that ties it to under the seat.

So here is what I suggest:

1. Once you are sure that the SRS alarm is caused by the seat sensor failure, remove the passenger front seat from the car, following the instructions at the beginning of this thread. (I disconnected the battery just for insurance)
2. Test the continuity for each of the 3 sensor wires from the connector to a place near the hole where the cable with those wires goes into the seat sensor box (not visible at this point). As I said before, if you were to be lucky to have a broken wire it will most likely be near the places where tie wraps attach the cable to under the seat.
3. If you find a broken wire then you have 2 options. Either bypass the broken wire using safe and proper procedures using multi strand wires with the same kind of insulation as the originals (note that this is not a trivial job for an amateur). Or replace the whole sensor anyways so as not to have patched wire works under the seat.
I chose to replace the sensor as I already had bought a new one. Yeah yeah I could have saved that $100, but I wanted to have all I could need when I decided to take the thing apart and the experts had already told me that the sensor was bad.

Incidentally, removing the leather cover from the cushion requires more than 1 person so that while one compresses the seat the other removes the bottom bar that attaches the leather to the base. The photo on this thread does show 2 guys doing that step and you need it so as not to damage the leather using tools to force your way. I was able to remove the leather without any tools or screw drivers with 2 people.

Do not remove the screw on the back of the seat, as indicated on the thread. The picture shows the screws all removed and the seat cushion completely off from the main assembly. I know why that was done, as connecting the clips to the wires on the leather is a tedious process , but if you follow the initial procedures using longscrew drivers to re-attach the leather wires to the clips you will have to disconnect a bunch of wires, including the seat belt clip sensor wires. I have seen many people who contributed with ideas on how to connect the clips to the wires, but they all require some trial and error. An idea just came to mind (maybe the thread starter did this way but did not provide details enough), if you were to flip up the bottom of the leather upwards you should then be able to see the wires and the clips and working from the back to the front hook them all. The leather is very tight at the bottom ends so this maybe difficult and the fishing method maybe the only one, but I find it hard to believe it was the way the seats were put together the first time.

The real tedious part is to have the seat assembly on the floor (use a carpet so that you don't scratch solid floors) and to try to work on the seat cushion while bending down. Ideally you should do this work with the seat assembly on top of a workbench or a table with some cover to protect it. That way you don't need to keep bending and can see the work better.

IMPORTANT: When routing the cables under the seat keep in mind that it moves up and down as well as forward and back so leave enough slack when using cable ties so that they don't get stretched or bent too hard, which would cause another failure very fast.

If you decide to do this work be patient , make sure you have the correct size star bits. Get someone to help removing the leather and have a beer at the end as you would have saved >400 in charges. If you take 4 hours to do this job then consider yourself a highly paid part time worker on a day off. Not bad. If you get your son to help you then make it one of those quality time father-son bonding moments we seem to have very little nowadays.

Now I am expert in fixing yet another MB problem I never had with any car in the past. Mind you I did not have many with electrically adjustable seats. LOL, but they did have MAF, Crank position sensors, etc and until I bought a MB I had problems with those before.