W203 SRS Warning Light - Loose Connectors Under Seat?

Benny Dub

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Afternoon All,

The SRS light has been on in my S203 C270 since we bought it about 6 months ago. Well MOT time is here so I should probably have a look.

My fiance's MG ZR has almost continuous SRS issues due to the crappy connectors under the seats coming loose - give them a wiggle, or tape them up, and the light goes off again, so I'm not usually bothered, but the Merc has me a little concerned.

I've had a look and the connector on the driver's seat looks fine, and at first glance so does the passenger's as well, however I had a closer look and it appears the plastic connector is quite loose - but the cables themselves are secure in the socket - see pictures below.


Yes yes, I know it's filthy down there!

Is this likely to cause the SRS light being on? From what I've read even after an issue is resolved you need STAR to turn the SRS light off, which makes diagnosing the problem a real pain. I'd rather not pay to get diagnostics done if I can help it, I have a basic OBD tool but it's not showing anything relating to the SRS light. Any thing else I can try to diagnose the issue?

As it's been on since we bought the car I can't tell what caused it to coe on in the first place, so I'm a bit in the dark as to what it might be.

Cheers
Ben
 

LostKiwi

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That connector shouldn't come apart like that.
Its quite possible the connector may be your issue though more often the seat occupancy sensor (if fitted) fails and triggers the SRS light. People kneeling on the seat or putting heavy boxes often break the sensor pad and the only way to repair it is to replace the pad. If it is that then you c an get emulators to fool the SRS system into thinking the pad is Ok but be aware that means the passenger airbag will always fire in the event of an accident whether the seat is occupied or not and that you cannot allow children to ride in the front seat as it can cause serious injuries.

The only way to be sure is to have the codes read. To do this you need a code reader thats built for Mercedes. Common ones are STAR, iCarsfoft MB v2.0, iCarsoft i980, CarSoft (as opposed to iCarsoft) or Launch x431 (I believe). Some people have had good results using Carly but check your vehicle is supported and has the SRS module supported.
 

EmilysDad

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In my experience, SRS/airbag light faults will need clearing even when they're fixed eg I removed the wiring from my driver's seat (to replace the battery), when I reconnected it I had the SRS warning which then cleared OK
 

Rory

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Common on MBs for the clockspring wiring to go in the steering column. Had it on mine, but it happened when it was about 5yrs old and MB did it under goodwill, although the car was on the old ServicePlus scheme so that might have picked up the cost anyway.

I know you said you didn't want to pay for diagnostic but if it doesn't go after wiggling a couple of things, you're a bit stuck.
 
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Benny Dub

Benny Dub

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Thanks guys. I'm assuming if the seat occupancy sensor was faulty then the seatbelt warning light wouldn't come on?

This works fine - if I have a heavy bag on the passenger seat I get the warning light - must admit I haven't ever tried the driver's seat because the seat belt is always done up - I will try this to be sure.

Bugger. I'll see if Carly works with the existing wifi OBD dongle I've got for my iPhone, if not I'll see if any local garages or mechanics have the appropriate diagnostic tools.

What a pain in the arse!
 

LostKiwi

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Thanks guys. I'm assuming if the seat occupancy sensor was faulty then the seatbelt warning light wouldn't come on?

This works fine - if I have a heavy bag on the passenger seat I get the warning light - must admit I haven't ever tried the driver's seat because the seat belt is always done up - I will try this to be sure.

Bugger. I'll see if Carly works with the existing wifi OBD dongle I've got for my iPhone, if not I'll see if any local garages or mechanics have the appropriate diagnostic tools.

What a pain in the arse!
No if the pad is faulty no matter what you do the light stays on.
 

LostKiwi

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That's cool, but it does go off if no one is in the seat and/or the seat belt is done up. Surely that means it's working?
Ah we're talking at cross purposes. You're talking seat belt light and I'm talking SRS light.
 
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Benny Dub

Benny Dub

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Ah we're talking at cross purposes. You're talking seat belt light and I'm talking SRS light.
Ha that makes a bit more sense - so if the seatbelt light appears to work fine, surely that means the seat occupancy sensor is working correctly, so therefore I can rule that out of what might have caused the SRS light to come on?
 

LostKiwi

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Ha that makes a bit more sense - so if the seatbelt light appears to work fine, surely that means the seat occupancy sensor is working correctly, so therefore I can rule that out of what might have caused the SRS light to come on?
The only way to rule anything out is a diags session with a reader that can read the SRS system.
 
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Benny Dub

Benny Dub

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MOT was today and it failed on SRS and some other stuff that's not too troubling. The garage had a Merc diagnostic tool (not sure whether it's STAR or not) and ran a check, note on the invoice when I picked it up was "Multiple error codes on airbag ECU, suspected faulty airbag ECU"

Haven't got a list of the codes, not sure whether to believe it or not, are Airbag ECU faults common? Anyone got any experience with this stuff?

Garage told me to scrap the car! Not planning on doing this obviously but would rather it didn't cost the earth to sort out either...
 


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