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Photo DIY - SRS Seat Sensor replacement

358293 Views 157 Replies 77 Participants Last post by  caleno69
Your SRS light has come on and stays on, Also you noticed that the airbag off light stays on as well. Your car has never been in an accident, and your bags and belts have never deployed. You have some basic mechanical aptitude and don’t want to pay a dealer 500-800 $US for this repair. Read On…
It is not necessary but best to look for an independent mechanic shop that displays the 'pie', and have the codes read, this will tell you exactly what the problem is. Most will not charge for this service, and unless you have the MB software and can read the exact pin, you can’t do it..

Lets try and address the most common questions regarding this condition.

Q; - Is this a safety issue, the car still runs and a friend of mine who has a 2000 210 has a piece of electrical tape over the light and just drives it. Do the air bags still work?

A; No, Operation of all SRS devices are unpredictable, they may not fire at all, or they may fire for no reason

Q; How many Sensors are there and where are they?

A; Many.. The SRS system has a pre-tensioner in each seat belt, several air bags, sensors throughout the car to activate same, and a child sensor in the front passenger seat.

Q; Before I tear my car apart I would like to know as much as I can, what the module looks like and yhe functionality and design information

A; The child sensor adjusts air bag and seat belt level for the front passenger, and effects the functionality of several other devices.

Q; Is a sensor of some kind in the drivers seat?

A: No, a seat belt switch, and seat belt tensioner , and air bags.

Q; If I replace the Ass Mass will the light go off?

A; BE Clear Here, when you fix the fault, The Light WILL go off by itself if all faults have been corrected.

Q; How do I do this repair myself?

A; On the next posts, you will see a series of pics, but the procedure is,,,
1. At some point, have the codes read, by an inde, (PIC 1 ) as having the seat pad SRS light on will 'MASK' other ( emergency tensioning retractor belt and bag) faults.
2. Buy a NEW sensor first, (PIC 2 ) I have not seen ANY signs of wear ( wires, scraping, breaks ) at all. The sensor 'dots' fail with use/age. Sensors cost 140 US$ at MB.
3. TIP- Take the seat out of the car, period. If you have never done one, and are not an MB tech, or leather repair expert, 5 bolts and some clips and the seat is out. Don't even try to in car cover remove. you will me$$ it up!
4. TIP- Allow an extra 2 hours to shampoo the carpet under BOTH front seats. which is what you will do when you see all the gack under the seat. My car gets 'mini detailed' weekly and it still had lots of filth under the seat(s). Record amount of coins found so far.. $16.83 US$’
5. Unplug all wires from the connector block (PIC 6-7 )
6. Snap off the bolt covers (PIC 8 )
7. Remove all four 'Torx' type bolts (PIC 9-10 )that secure seat rails in place on the car floor.
8. Pull OUT not up on seat belt bolt cover(PIC 11 ) and remove bolt.
9. Release the wire cable (PIC 12 )
10. Tip the seat top down and remove the complete car seat from the car.
11. Remove the connector block and unplug the yellow sensor (PIC 13 ) connector from it's housing under the seat.
12.Take off the plastic side covers.
13. Loosen the 2 back bolts, (PIC 14-15 ) and remove the 2 front ones, This is optional and done to make the job easier.
14. Push down on the leather, (PIC 16-17 ) and pull out the bar that holds it to the frame.
15. Twist 90 degrees on the plastic ‘butterfly’ clips, (PIC 18-19-20 ) and release the leather cover.
16. Change out the sensor pad (PIC 21-22-23 ).
17. Once you have removed the sensor pad unit replacement is simply a reverse procedure. (PIC 24-25-26 )


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· Registered
E 350 2016 second one. actually 3rd as I bought one for daughter, since sold.
125 Posts
air bag sensors, on the fritz

If I read this right, the problem is more likely the wires than the sensors, yes?
Well will the code readout tell us that?
Or do I ask the mechanic to change the gizmo and look at the wires? Since he will have to remove seat in order to see it all anyway and it seems like hundreds for the labor and a hundred for the device? Crackie!

much obliged, cover me I am going in guys,


· Registered
E 350 2016 second one. actually 3rd as I bought one for daughter, since sold.
125 Posts
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,


· Registered
E 350 2016 second one. actually 3rd as I bought one for daughter, since sold.
125 Posts
I chickened out

So far I have gotten the diagnostics, yes I need to fix it.
I went to a local upholsterer who has the Benz symbol on his card.
He offered to do the work for $20 hour. I get the pad.
At that point I froze.
As long as this is my work Benz (outside sales) I aint going to mess with it.
Maybe when I retire, joke.
Anyone want to reinvigorate me?

Much obliged,

Jeffinski Max

· Registered
E 350 2016 second one. actually 3rd as I bought one for daughter, since sold.
125 Posts
Done, seat sensor.

Weeeeelll, I wasnt thrilled with the idea of taking apart the seat and replacing the sensor myself. As my work vehicle I need it to run Mon-Fri. with no doubts. And we all know what happens when one starts an unknown project. So I followed this thread for many months. Always with a eye to finding a simpler was. But with out paying $5-600.00 US to get the job done. And that was at my off-Benz mechanic.
So the other day while at a body shop I enquired if he know of anyone who specialized in this work.
The proper term seems to be: SEAT SENSOR
And yes he did give me the name of a mobile company who did the work for MB dealers and body shops.
The fellow had me order the part from MB. $200. later he he and the part show up in my driveway (seperately).
It was the wrong part, this despite that I ordered it with the VIN number in hand.
Back to MB. This time I am in the wholesale parts dept. $350. later I have a totally different module of which my seat has four, one in each corner of the front passenger seat. As well as a master module. Heaven only knows how much all of it would have cost. Or should I say hell.
$350.+225.00 install=$575.00 happy camper. Glad I did it. Glad I did it this way. Good luck to you all. And my thanks to Mr. Smith otherwise I would have never started at all. Hmmmm.

Much obiged,

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