E420 SRS Light question
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Junior Member
Joined: Jun 2005
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2002 E430 4MATIC
E420 SRS Light question
My SRS light comes on when ever anyone sits on the passenger seat. It goes off as soon as they get out. I guess it has something to do with a child safety system from what I read. Most people have the light come on and stay on. Mine is off and comes on when anyone sits on the seat.
Is it just a bad connection or do I have to replace the sensor under the seat? How safe is it to work on the SRS system and does anyone have any directions? I don't want to try to save a couple of bucks and set of the air bag; if you know what I mean.
Thanks
Is it just a bad connection or do I have to replace the sensor under the seat? How safe is it to work on the SRS system and does anyone have any directions? I don't want to try to save a couple of bucks and set of the air bag; if you know what I mean.
Thanks
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John Deere
How light is your passenger? As far as I understand, the light should come on if you put the equivalent of a child and baby seat, let's say 5 to 40 pounds. The light on indicates the passenger airbag is off so that the child is not crushed.
But if the light comes on for larger passengers, it would indicate a malfunction in the sensor itself or the wiring may be loose. Really hard to say without taking off the seat cover. I suppose you could first try reaching underneath and ensuring the wiring connections are all tightly seated. Though given the history of these sensors, it may come down to replacement.
DIY will take a few hours with a $200 sensor. You need to unbolt the seat anchors, 2 in front and 2 in back, pull out the seat, then peel off the leather. The sensor itself is a plastic pancake that unplugs from the wiring harness.
I can't give more detail because it was explained to me verbally by someone who had already done it. Perhaps someone else can add to this.
But if the light comes on for larger passengers, it would indicate a malfunction in the sensor itself or the wiring may be loose. Really hard to say without taking off the seat cover. I suppose you could first try reaching underneath and ensuring the wiring connections are all tightly seated. Though given the history of these sensors, it may come down to replacement.
DIY will take a few hours with a $200 sensor. You need to unbolt the seat anchors, 2 in front and 2 in back, pull out the seat, then peel off the leather. The sensor itself is a plastic pancake that unplugs from the wiring harness.
I can't give more detail because it was explained to me verbally by someone who had already done it. Perhaps someone else can add to this.
Senior Member
Joined: Apr 2006
Posts: 463
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From: Long Island, NY
01 E320
My SRS light comes on when ever anyone sits on the passenger seat. It goes off as soon as they get out. I guess it has something to do with a child safety system from what I read. Most people have the light come on and stay on. Mine is off and comes on when anyone sits on the seat.
Is it just a bad connection or do I have to replace the sensor under the seat? How safe is it to work on the SRS system and does anyone have any directions? I don't want to try to save a couple of bucks and set of the air bag; if you know what I mean.
Thanks
Is it just a bad connection or do I have to replace the sensor under the seat? How safe is it to work on the SRS system and does anyone have any directions? I don't want to try to save a couple of bucks and set of the air bag; if you know what I mean.
Thanks
The passenger seat occupant sensor is mounted underneath the leather. The seat has to be removed, and the leather removed from the seat. My friend owns a seat upholstery shop and he did it in less then half an hour for $40. The part cost me $130 online. Actually what failed on mine (and probably yours) is the wire between the sensor and the harness underneath the seat. The rocket scientists at mercedes strap the wire tightly to a sharp edge underneath the seat and everytime a passenger sits down, it pushes pressure on the wire. Eventually it cuts through and you get the condition you described. There is no way to bypass the sensor because its a totally over engineered data signal device.
The best I can tell it is only useful if your using a Mercedes Infant car seat that plugs into the harness. The passenger airbag off light doesnt come on if there is no passenger like it does on newer american cars. In other words, it's a totally useless, over engineered system that frequently fails and costs Mercedes owners big bucks. A system for an infant car seat THAT SHOULD BE IN THE BACK SEAT ANYWAY. Dealers get about 600 for the repair.
That said, I still love me E320 :-)
Thread Starter
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2002 E430 4MATIC
The light comes on when an adult sits in the seat and goes off when no one is there. So it is like it is working but not right. You would think if it was a loose wire it would not detect anything or the light would stay lit the whole time?
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John Deere
The passenger seat occupant sensor is mounted underneath the leather. The seat has to be removed, and the leather removed from the seat. My friend owns a seat upholstery shop and he did it in less then half an hour for $40. The part cost me $130 online. Actually what failed on mine (and probably yours) is the wire between the sensor and the harness underneath the seat. The rocket scientists at mercedes strap the wire tightly to a sharp edge underneath the seat and everytime a passenger sits down, it pushes pressure on the wire. Eventually it cuts through and you get the condition you described. There is no way to bypass the sensor because its a totally over engineered data signal device.
The best I can tell it is only useful if your using a Mercedes Infant car seat that plugs into the harness. The passenger airbag off light doesnt come on if there is no passenger like it does on newer american cars. In other words, it's a totally useless, over engineered system that frequently fails and costs Mercedes owners big bucks. A system for an infant car seat THAT SHOULD BE IN THE BACK SEAT ANYWAY. Dealers get about 600 for the repair.
That said, I still love me E320 :-)
The best I can tell it is only useful if your using a Mercedes Infant car seat that plugs into the harness. The passenger airbag off light doesnt come on if there is no passenger like it does on newer american cars. In other words, it's a totally useless, over engineered system that frequently fails and costs Mercedes owners big bucks. A system for an infant car seat THAT SHOULD BE IN THE BACK SEAT ANYWAY. Dealers get about 600 for the repair.
That said, I still love me E320 :-)
Totally agree about the back seat point.
Is it possible to repair the wire by splicing it back together?
Senior Member
Joined: Apr 2006
Posts: 463
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From: Long Island, NY
01 E320
The symptom you have with the light going on when someone sits down is exactly what I had. Also the Passenger Airbag off light in the center console goes on. When it is working correctly that light only come on for a few moments on startup. Never any other time.
Senior Member
Joined: Apr 2006
Posts: 463
Likes: 8
From: Long Island, NY
01 E320
It wasnt a loose wire. The wire comes straight down from the sensor and is strapped tightly with a wire strap to a hole in the bottom of the seat. Evertime someone sits down, the wire is pushed down towards the strap and the wire bends across the sharp edge. eventually it cuts through the wire.You can feel the wire under the seat and when I cut away the wire strap, I was able to feel a slight cut in the wire. That was the problem. The connector plug for the sensor at the bottom of the seat is the yellow connector. Airbag sensors always have yellow connectors
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2002 E430 4MATIC
Thanks for the ideas, I'll try to take a look at it this weekend and I'll let you know what I find. Better to be armed with a little information then to go at it with nothing.
Thanks!
Thanks!
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MBWorld Fanatic!
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From: SF
07 E63 06 CLK55 Cab 03 P-car C4S
also, does the SRS light being "on" constantly mean that even with a passenger in front passenger seat, that the airbag WILL NOT DEPLOY in crash?
thx all.
