Electrical issues after CAT S

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whatajob

New Member
Joined
Sep 28, 2023
Messages
8
Location
Eastbourne
Car
Mercedes C220
Hi guys hoping someone here might be able to shed a little light on an electrical problem I've got

Not long ago I bought a 2012 C220 estate online which was previously a CAT S write off. The guy I bought it from did most of the work needed just to put it on the road (front bumper, radiator, off side wishbone, suspension and some other bits and bobs)

The problems I have are now a fault is coming up on the dash for hood open, brake fluid low, coolant low and the front indicators aren't working. I've shorted out the plugs to these to close the circuit and the errors are still there which would indicate to me that there is a brake in the wiring further into the engine somewhere.

But then I was thinking, how likely is it that all the associated wires would be broken (assuming its damaged caused by the write off) is there a chance that they could share a common earth somewhere? maybe broken during a front end collision?

Other than the faults its a lovely car with low mileage and would be great to get it back on the road and to its former glory :)

Any ideas anyone?

Thanks for your time
 
Possibly a fault with the front SAM. Shorting across the pins of plugs is not a good idea as modern cars use bi-directional wiring. You could cause damage to other non related modules by doing this, Star diagnosis would be a better option.
 
Possibly a fault with the front SAM. Shorting across the pins of plugs is not a good idea as modern cars use bi-directional wiring. You could cause damage to other non related modules by doing this, Star diagnosis would be a better option.
Thanks John

After your advice which really is appreciated I have taken out the front SAM and had a good look at it and all the wires that plug into it, all 'seems' in good condition - I did read somewhere that water ingress can damage the pcb so checked that too. Plugged it all back together and problem still exists (no surprise really).

I hear what you say about a star diagnostics and makes sense but was wondering, would the diagnostics tell me if I had a faulty SAM? I don't own a star scanner but can buy one
 
Thanks John

After your advice which really is appreciated I have taken out the front SAM and had a good look at it and all the wires that plug into it, all 'seems' in good condition - I did read somewhere that water ingress can damage the pcb so checked that too. Plugged it all back together and problem still exists (no surprise really).

I hear what you say about a star diagnostics and makes sense but was wondering, would the diagnostics tell me if I had a faulty SAM? I don't own a star scanner but can buy one


A short circuit on the wires can damage the front SAM. Another possibility is that a wiring loom was damaged, that happens to run the wires to all those circuits.

You can't buy a genuine STAR as a private individual (thought there are Chinese clones on eBay), instead you'll need to take the car to an independent specialist who has Genuine STAR.
 
You're in Eastbourne,

Can the forum advise options for the OP on a capable indi with STAR?
 
Update - have listened to advice (thank you) and taken the car to a local specialist and in a nut shell have concluded that the front SAM is indeed at fault! They have managed to clear all faults displaying apart from the hood open as they where historic - presumably due to the forementioned front end collision. Embarrassingly enough though the front indicators aren't working because there are no darn bulbs :oops: mind boggles how he managed to get it through an MOT like that but oh well..

So the company has now quoted me for the repair and I know I'm going to sound like a skinflint but sort of want to do it myself - the quote was shall we say, north of what I expected to pay! I have seen a unit for sale on ebay for an affordable price but was wondering, would the SAM unit needed to be recoded even if the part numbers are the same? I'm getting conflicting opinion on this

Thanks in advance :)
 
I've just had another thought is there a chance I could have the SAM repaired? That would be cool
 
You need to code the front SAM for the options on the car, i.e you'll need online Xentry Diagnosis - or be very lucky and get a Sam from a car with exactly the same options, Sam controls lights, engine cooling fans etc etc etc etc., Having the same part number is no use to you.

Did your independent actually check the ground leads as-well as the signal leads ?

As this was a structural write off (CAT-S) and he managed to get the car through a MOT without indicator bulbs I'd be getting an independent check of his work and that its not going to kill you in a small crash because clearly whoever repaired it has a dodgy MOT man and probably a dodgy attitude to your safety,
 
I see what you are saying regarding the SAM needing to be coded, would I then be right in assuming that any used SAM would be ok providing the connections are all the same and then have it programmed to my car? The specialist I took it to has quoted me for a new one from MB at an eyewatering cost and I see these used for sale on ebay for a fraction of the price - could I potentially buy one of these and have someone code it for me? I'm very sure the place that diagnosed the faulty SAM wouldn't entertain the idea of fitting one they haven't supplied (understandably so) so would have to find someone to code it for me

Its a bit frustrating to replace the unit when all that seems wrong with it now is the hood open warning coming up on the dash, makes me wonder if that can be bypassed or something...

Absolutely agree by the way regarding the MOT, I highly suspect the guy I bought it from put a dodgy one on it! I did get someone to give the car a once over to make sure it was safe to drive but when all fixed (hopefully) I'll probably re MOT it just to be on the safe side

Thanks for all the help so far, it's really appreciated :)
 
There are different hardware revisions of the SAM the behave differently. Theres also a lot of broken SAMs on eBay. If you must go used, get one with same part number. You need someone with online Xentry Diagnosis to code it (i.e genuine supported Mercedes diagnosis as it goes online to get the coding from Mercedes directly and part of installing a new part is to upgrade the firmware to latest version too (which Xenrty will do). Most people won't code parts they haven't supplied,

I'd be checking the wiring, switch etc for the hood (its on the left bonnet catch) - strange that only 1 input has failed on the SAM and its an input that gets grounded (so hard for it to be damaged in an accident where normally things get shorted to ground) before replacing the SAM though. If you can get to M3 Junction 3, go see www.comand.co.uk

I'd be getting someone with more structural expertise than just an MOT station given the repairers willingness to put a dodgy MOT on it. (and I believe it shouldn't have passed with any warning messages!!)

Cheers
Richard
 
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May or may not help,

Seems strange that its only showing one error, It suggest to me the problem is more likely electro mechanical rather than the SAM module. I would be tempted to investigate further into the bonnet latch switches and mechanism before looking to replace the SAM module. Just to be 100% sure if nothing else.
 
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May or may not help,

Seems strange that its only showing one error, It suggest to me the problem is more likely electro mechanical rather than the SAM module. I would be tempted to investigate further into the bonnet latch switches and mechanism before looking to replace the SAM module. Just to be 100% sure if nothing else.
Thanks, I have watched this video before actually but just watched it again in case I missed anything - regrettably I didn't. What I did try is making the contacts on each bonnet sensor wire to emulate them being closed, maybe that's not a good enough test...
 
So guys I took the front bumper off to replace the missing parking sensors and noticed this little guy just hanging there all on his lonesome, anyone have any ideas what its for? Optional front fogs perhaps? A part of me is secretly hoping its bonnet sensor related however unlikely, oh, not a secret anymore I guess! The larger plug is for the parking sensors

As you can probably see the guy who did the work for the CAT S couldn't even be bothered to clean up before replacing the bumper :rolleyes: I will most certainly have this thoroughly checked over before taking it on the road

I really do appreciate all your help guys, even if I don't manage to get this fixed you've made me feel less alone with this :)

wire.jpg
 
Can you post a pic of your bumper? That plug looks like the Day Running Light connector: your S204 should have either DRLs or foglights built in as a standard depending on the which model it is.
 
It's not the Day Running Light connector, there are 2 separate wires going in to them. Sorry probably should have mentioned that. There is no device on the bumper that the plug could possibly feed. Possibly the old bumper prior to replacement had a pair of those fancy head light washers or something like that...
 
May also be useful to put your VIN in vindecoderz to check what options you have (or should have) on the car. Possibly a different front bumper was fitted after the crash
kc
 
It's not the Day Running Light connector, there are 2 separate wires going in to them. Sorry probably should have mentioned that. There is no device on the bumper that the plug could possibly feed. Possibly the old bumper prior to replacement had a pair of those fancy head light washers or something like that...
Strange.
On my 2013 S204 the DRL's definitely had a 2 pin connector just like the one in your pic.
 

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