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2003 W209 CLK200 Kompressor Coupe
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Discussion Starter #1
Hi,
I've searched in the forum for SRS related issues. I haven't found something similar to mine, but excuse me if I missed it.
So, a couple of days ago I accidentally discovered that one of the yellow connections underneath the passenger seat (left hand side in my country) was disconnected, but I never had an SRS light on, nor a Malfunction on the Multi-function display.
So I tried connecting it and then the SRS light came on and I also had 1 Malfunction "SRS - Restraint System Service". The "Airbag OFF" light on the centre console remained off at all times. When I disconnected it again, the SRS light and the Malfunction message both went off and everything seemed normal as before. In the first two pictures below you can see the wiring and the connections underneath the seat taken from the front. The last two pictures are taken from underneath the seat from the back. The disconnected connection as seen from underneath the seat is the one with the brown, white and red wires.

Now, two more things I need to tell is that when the passengers don't fasten their seatbelt I have no warnings (whereas on the driver's side there is a warning), which I found weird because my cousin had the same model (but later year) and on his car there was a warning when the passenger didn't fasten their seatbelt. Also when my mechanic plugged the car onto the STAR he told me that the child seat sensor (or whatever it's called) inside the passenger seat is not functioning properly.

It makes sense to me that replacing the child seat sensor will fix this issue. However, is there any case (from your experience) that it's not the sensor itself but any of the wires that are causing this problem?

Also, a more important question: Is the SRS system still functioning properly if the SRS light is off and the wiring underneath the seat is disconnected, as it has been since I had the car? Because if I am 100% completely sure that the SRS system is working properly, I might not get into replacing the sensor since I don't plan to ever put a child seat on the front seat.

Thanks for the feedback.

Chris
 

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Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
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That's the wiring harness for the occupancy sensor on the passenger seat. I suspect that it is defective and so a previous owner just disconnected it. I am a bit surprised that with it disconnected that you don't get an SRS error, but I guess that is some sort of fail-safe function. BTW, with it disconnected, what does the "Passenger Airbag OFF" light do? If it is not illuminated, then the system would assume there is a passenger there and in the event of an accident, the airbag would deploy.
 
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2003 W209 CLK200 Kompressor Coupe
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Discussion Starter #3
Hi again,
Thanks for the reply. The "Passenger Airbag OFF" light located on the centre console is NOT illuminated. It only comes on when I first turn the key to position 2 and then turns off when I start the engine, regardless of the wiring harness being connected or not.

If it is not illuminated, then the system would assume there is a passenger there and in the event of an accident, the airbag would deploy.
But, if the system assumed there is a passenger there, wouldn't I get a visual and audible warning when the passenger does not fasten their seatbelt? Or I don't get it because of the faulty occupancy sensor?

Chris
 

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This is just a guess, but with the sensor unplugged, it might go into some sort of default mode where the airbags are enabled (thus the "Passenger Airbag OFF" indicator is extinguished) but the seat belt warning does not engage. How annoying would it be to drive around with that going off!
 

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2004 CLK 240 Coupe
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11,379 Posts
But, if the system assumed there is a passenger there, wouldn't I get a visual and audible warning when the passenger does not fasten their seatbelt? Or I don't get it because of the faulty occupancy sensor?
Interesting question.

I think that the seatbelt alarm on the driver's side operates if the car moves several yards without the belt being buckled. There is no seat occupancy sensor on the driver's seat, so the system must assume that the driver is on the his seat.

For the passenger seatbelt, maybe the occupancy sensor, designed for the airbag inhibit, is also used for the seatbelt buckled confirmation.

Certainly, without a passenger the seatbelt alarm does not go off. I cannot remember if a seated passenger does not buckle up, the seatbelt alarm goes off.
 

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2003 W209 CLK200 Kompressor Coupe
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Discussion Starter #6
This is just a guess, but with the sensor unplugged, it might go into some sort of default mode where the airbags are enabled (thus the "Passenger Airbag OFF" indicator is extinguished) but the seat belt warning does not engage.
I also hope that it's like this, because this is really a safety issue.

Interesting question.
I cannot remember if a seated passenger does not buckle up, the seatbelt alarm goes off.
So, you also don't get a seatbelt alarm when a passenger gets into your car and does not buckle up?
I'm not putting my hand on fire, but I think that when I once got into my cousin's 2004 CLK as a passenger, the seatbelt alarm went off as soon as the car was moving until I buckled up...
 

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2008 CLK350 Cab.
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My 2008 cab. will sound the seat alarm if the passenger seat occupant does not buckle up after the car starts moving.
 

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2004 CLK 240 Coupe
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So, you also don't get a seatbelt alarm when a passenger gets into your car and does not buckle up?
My normal front seat passenger is my dog..:)

His harness is clipped into the seat belt fixed buckle using a short adaptor. At 12kg, I'm surprised that he is heavy enough to trigger the seat occupied sensor.
 

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2004 CLK 240 Coupe
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11,379 Posts
I did an experiment yesterday with my dog Chester in the front passenger seat.

Whether buckled in, or not, the seat belt alarm did not sound off during driving. I'll try it later with a human..:)
 

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Chester does not look very happy. I hope you appropriately compensated him for his hard work in your experiments. Maybe you lowered his window so he could hang his head out? :)
 

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BenzWorld Elitist
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Separated at birth?

 
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2003 W209 CLK200 Kompressor Coupe
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Discussion Starter #13
I know it's been quite some time since I started this thread, but I would like to share something more about this.
So, one day I was reading the manual of the car and I found out that the child recognition sensor (CRS) on the passenger is actually an option, at least for European cars, I don't know about the rest. In the manual it states clearly that vehicles not equipped with CRS have a distinctive sticker at the side of the dashboard, visible when opening the passenger's door which indicates that an airbag is ON and it's not safe placing a child seat on the front passenger seat. It also says that the AIRBAG OFF light in the center console still lights up when key is turned to position 2 even in vehicles not equipped with CRS and it goes away when the engine starts. My car has that sticker, and also the light behaves as the manual explains, so I tend to believe that I don't have the CRS after all. I assume the disconnected cable I have under the seat is the one connecting the CRS if present, and therefore being disconnected is its normal state so I guess the SRS system functions properly all the time. Is this a sane assumption?
Anyone else with the side sticker + disconnected cable under the passenger seat?

Chris
 

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2004 CLK 240 Coupe
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So, one day I was reading the manual of the car and I found out that the child recognition sensor (CRS) on the passenger is actually an option, at least for European cars, I don't know about the rest. In the manual it states clearly that vehicles not equipped with CRS have a distinctive sticker at the side of the dashboard, visible when opening the passenger's door which indicates that an airbag is ON and it's not safe placing a child seat on the front passenger seat.
Maybe the CRS design changed later. My 2004 Owner's Manual desribes the Automatic Child Recognition System in which if the special MB child seat is fitted, this will inhibit the passenger seat airbag operation.

PS. I've just noticed Marden's hilarious post 12 above.
 

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2003 W209 CLK200 Kompressor Coupe
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Discussion Starter #15
Maybe the CRS design changed later.
Maybe. I think my car actually came from one of the initial production lines of the W209 type (production date is 02 Jan 2002) so maybe at that early point the CRS was really an option.
 

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2004, CLK 320
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You may find they placed a Sensor Bybass, or a Seat Occupancy Occupation Sensor SRS Emulator for Mercedes-Benz Type6(2000-2005) you can buy these from most electrical stores or http://www.dhgate.com/product/seat-occupancy-occupation-sensor-srs-emulator , a link, it tell's the system you have a person in your seat and activates the air bag to deploy if an accident.
add on,
I have found out the SRS can all so an easy correction, unbolt your left seat, lift backword and see the yellow connectons, unclip so you can handle the cables, cut each cable one by one as you solder each one as you go, just help no incorrect cables mixed up. and you may find there is no problem any more, I did it to my CLK and SRS is gone. the cable connections get old and need to be replaced or ust solder up the cables, as how offen do you tack your seat out, ??? hope it was help full.
 

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MY05 CLK55 AMG ,CLK320,Former,C180 Kompressor,Jensen Healey,Ford Capri V6,Alfa GTV.
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Good idea...did you read my post from 12 days ago ? Restraint system service ..
 

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2004, CLK 320
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10 Posts
Yeap just a refresh, your photos a while back helped my problems, very appreciated. enjoy the weekend
 
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