SRS warning light

James16

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The SRS warning light on my 2003 (52 plate) C180 kompressor estate will not go out. My usual garage has tried two lots of diagnostics equipment to clear the fault but neither will talk to the control module. The suggestion is either a blown fuse, disconnected wire or SRS module has blown. Has anyone else had this problem? Is there any easy fix? Is there an easy way to get at the fuse or control module? The module is in the centre consol / dash, not sure where the fuse is? Any ideas would be great!
 

47p2

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Most common problem is a break in the circuit at the passenger seat. It could be the plug that has a poor connection under the seat but the most common problem is the seat pad
 
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James16

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Thanks, I'll have a root around under the seat. Is the seat pad any easy fix if that's the problem?
 

47p2

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It would be best having the car checked by Star.
 

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A loose wire on the connector under the seat, or broken wire on the Pad, or fault is seat belt buckle, all passenger side
 
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James16

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Thanks for the pointers.

This may be a daft question but who or what is star? Assuming it's some type of diagnostics, is there one located near north nottinghamshire?
 

television

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STAR is the official MB testing tool

You have MB tech in Mansfield a member on this forum, and that is just down the road from you
 

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The SRS warning light on my 2003 (52 plate) C180 kompressor estate will not go out. My usual garage has tried two lots of diagnostics equipment to clear the fault but neither will talk to the control module. The suggestion is either a blown fuse, disconnected wire or SRS module has blown. Has anyone else had this problem? Is there any easy fix? Is there an easy way to get at the fuse or control module? The module is in the centre consol / dash, not sure where the fuse is? Any ideas would be great!

There are a number of possible causes to this but as you cannot even contact the control module then thats the most likely.

I have even seen this warning come up when you remove the wire to the hazard warning lamps! And of course when I remove a steering wheel!
 

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There are a number of possible causes to this but as you cannot even contact the control module then thats the most likely.

I have even seen this warning come up when you remove the wire to the hazard warning lamps! And of course when I remove a steering wheel!

If the wheel is taken off, and the ignition turned on, this will store the SRS fault and only STAR can remove it, not otherwise. With intermittent faults where the SRS lamp is not on permanently, 99% are the above mentioned items in Post 5
 
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James16

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The car ahs been checked on STAR and this cannot communicate with the SRS ECU. Is the most likely cause still one of the passenger seat issues?
 

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Might be a SAM communication fault but more likely the SRS controller,,in this case ignore the seat faults as the lamp is permanently on
Wait till the other techies come on line
 

MB-Car-Tech

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James16,

I will find it hard to believe that a fuse has blown!!

There are 2 fuses in the drivers side fuse box unnder the bonnet (hood).

Fuse 49 and Fuse 45 - If you are lucky there will be a fuse location sheet in the Interior Fuse Box at the end of the dash panel - (open drivers door and remove plastic end covering - paper sheet !!)

What did the STAR test generate - were you provided with the test results.

This can be a great start to fix the fault !! The C Class (203) has CAN communications and the main controller here is the EIS (Ignition Switch) anyways......
the Test result will/should show multiple CAN communication messages from the SRS control module

Next step would be to expose the SRS module (located previously) and test the circuit to it and get the wiring diagram out !!!

Circuit 15 and 15R - this means voltage supplied to it when the ignition is on

Good Luck
 

nialler

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oh hang on mb, is the location of that map on all mercedes there? I was told it was under the spare wheel hence there's a lump of papier mache (sp?) there. Car's a w220 btw.
 

Alex Crow

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my approach would be as mb-car-tech. checking the k wire, earth and power supply at the srs ecu pins, if these check ok and no can is established it does suggest srs module failure, but an overview of all modules and faults should be done to ensure all other can comms etc are ok. same as mbcar tech really...
 

MB-Car-Tech

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nialler,

the fuse location chart is different for the W220.

There should be a sheet in the boot (trunk) with the tool kit tray.

But as we all know - very rarely are they still there !! normally just thrown away as rubbish !!
 
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James16

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Thanks everyoen for the pointers.

Can anyone send me a copy of the workshop manual pages for accessing and changing the SRS ECU and also the wiring diagram for it?

Cheers

James.
 
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James16

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I have changed the SRS ECU for one from a breakers. This now talks to the diagnostics but still shows a fault as it is locked to the chassis number of the vehicle it came out of.

Does anyone know how to overcome this problem or where I could get either the replacement or original ECU reconfigured or repaired?
 

Alex Crow

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can you confirm the replacement will talk to the diagnostics you are using? if so, try plugging the old one in again - sometimes just unplugging and refitting will help.
 


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