W205 C-class Adblue fault damaged wire

[SammyG]

Hi All,

Just wondered if has anyone else has a fault with the Adblue systems, that brings on a Check Engine Light and then you get a 500mile count down until the car won't start.

I had this issue and it turned out to be a faulty wire that a manufacturing defect had rubbed through the wire causing a Tamper fault code. The fault indicated that the Adbule system was being Tampered with and causing the 500mile shutdown message.

Apparently, this is a common fault, anyone else seen this?

 

[Nikolacz]

I have the exact same problem today on my 2015 c220. Merc are saying that I’ve to pay £380 as it’s just wear!

 

[elan362]

Hi All,

Just wondered if has anyone else has a fault with the Adblue systems, that brings on a Check Engine Light and then you get a 500mile count down until the car won't start.

I had this issue and it turned out to be a faulty wire that a manufacturing defect had rubbed through the wire causing a Tamper fault code. The fault indicated that the Adbule system was being Tampered with and causing the 500mile shutdown message.

Apparently, this is a common fault, anyone else seen this?

where is the affected wire that rubs through?

• in the engine bay?
• under the car?
• buried in the loom?
• behind the dash?
• is it accessible?
• can you identify it (perhaps with a photo or 2?) for others so others (myself included) can inspect and can take steps to protect / prevent chaffing through?

if it is a common fault - then it would be worth inspecting / protecting as a precautionary measure.
Thanks

 

[Nikolacz]

So, Mercedes have said this is wear and tear. This is apparently a section of cabling at the top end of the ad blue system. The engine light came on, next day the adblue lights on. Top up the adblue as I should, engine light and countdown won’t go. I bought the car at Maklin Motors, they towed it to Mercedes as the miles has run down so much on the no-start countdown. Merc say that this is wear and tear and I’ve to pay £400 for them to repair a section of cable. They said this can’t guarantee that the engine light will go away though and that there maybe more issues. They said the nox sensors are fine and those would be changed free of charge anyway if they did happen to be faulty.

I asked for a photo of the issue, they won’t cover the costs and say that because it’s from a dealership, they won’t absorb the costs. I asked for an explanation as to how the wiring loom has been chaffed. 6 times I’ve asked and no answer yet.

So I decided I hate Mercedes afterall and that I’d change car because I’m only 8 months into this pcp deal on the merc. The Nissan garage where I’m looking at the Leaf tells me that they are owned by the same people as the Mercedes garage that I’m currently dealing with. The salesman at Nissan begins communications with merc and they then tell him that they won’t fix my car for free because they believe at some point it has been worked on at a non Mercedes garage and someone has nicked the cabling. They won’t tell me that because it’s not true. The car has a full service history with Mercedes and right before I bought it, it was services at a Mercedes garage. Mercedes have told me that these things happen due to the nature of outside causes....despite telling me that the damaged cable is tucked behind a protective undercarriage tray. It sounds like a contradiction to me. I’ve logged a Mercedes complaint but I’m not hopeful.

I loved my car and now I will never ever buy another Mercedes. I will talk sh*t about them to whom ever will listen lol.

I’ve gone electric and bought a leaf, Nissan have paid for the work and obviously that means I have because it’s built into my new finance deal. At this point I don’t care and want rid of this car that tricked me with its good looks, it’s a pile of problems both inside and out.

 

[Mikesmith29]

It looks it's been rubbing on something for awhile and eventually rubbed through the sheathing.

However unless it's shorting out against something else I would not expect a bare wire to cause a fault unless it has physically broken.

Where is this actually situated on the car?

 

[Deleted member 149005]

£400 to repair is a lot less than the cost to change...

 

[Deleted member 149005]

£400 to repair is a lot less than the cost to change...

 

[Nikolacz]

£400 to repair is a lot less than the cost to change...

Yeah, true. But I fear it was just the beginning of the problems. It needed three new tyre and an mot coming up. I’ve pretty much gotten the leaf for the same monthly cost as the Mercedes. No mot coming up now and am going to save about £60 a week on diesel. I’ve had the Mercedes for 8 months and had so many little things go wrong. Computer constantly freezing which is way more frustrating than it sounds, it doesn’t even allow the cameras to operate, can’t turn volume down, can’t change station or even turn off. Puddle lights have gone out one by one until now none of them work. Weird noises through the heaters, sounds like crickets. It’s crap because it’s a lovely looking car, I will miss it but I will not miss the continuous communication with dealerships/manufacturers.

 

[Nikolacz]

It looks it's been rubbing on something for awhile and eventually rubbed through the sheathing.

However unless it's shorting out against something else I would not expect a bare wire to cause a fault unless it has physically broken.

Where is this actually situated on the car?

It’s hard to say where the broken cable is situated because I haven’t been able to actually be there to see. Mercedes are just telling me that it’s at the opposite end of the adblue system.

 

[Nikolacz]

It’s hard to say where the broken cable is situated because I haven’t been able to actually be there to see. Mercedes are just telling me that it’s at the opposite end of the adblue system.

I means opposite end to the nox sensors

 

[Mark0x]

Had the same problem on a 2016 W205 C220d, attached the faults in case it might be helpful to anyone experiencing similar.

Went to start car and it almost didn't start, felt like the battery was almost flat (maybe when the broken wire initially shorted?). Drove okay after that for that journey and a later journey, then next day the CEL came on.

Local-ish indy found the fault and repaired the broken wire, £300.

 

[zipdip]

I can understand your anger at Mercedes,they are fast becoming the Arthur Daly of the motor trade,what is showing up is that everybody on this forum who has a ad blue car had better check that wiring it seems to be a fault either in running that cable or it being badly installed .

 

[Johngoode]

Hi All,

Just wondered if has anyone else has a fault with the Adblue systems, that brings on a Check Engine Light and then you get a 500mile count down until the car won't start.

I had this issue and it turned out to be a faulty wire that a manufacturing defect had rubbed through the wire causing a Tamper fault code. The fault indicated that the Adbule system was being Tampered with and causing the 500mile shutdown message.

Apparently, this is a common fault, anyone else seen this?

I have a mercedesbenz c220 bluetech 2015 had the same problem engine light came on followed by 400 miles countdown for adblue after engine will not start took to hull mercedesbenz the fault was a rubbing wire at the bottom of adblue tank which cost £250 to repair which is not covered by my extended warranty this is just a ticking time bomb for anybody owning these cars this is bad design to have a harness on corner of a tank with no clips to hold it or extra protection who can you complain to it needs looking at

 

[Johngoode]

I have a mercedesbenz c220 bluetech 2015 had the same problem engine light came on followed by 400 miles countdown for adblue after engine will not start took to hull mercedesbenz the fault was a rubbing wire at the bottom of adblue tank which cost £250 to repair which is not covered by my extended warranty this is just a ticking time bomb for anybody owning these cars this is bad design to have a harness on corner of a tank with no clips to hold it or extra protection who can you complain to it needs looking at

I have a mercedesbenz c220 bluetech 2015 had the same problem engine light came on followed by 400 miles countdown for adblue after engine will not start took to hull mercedesbenz the fault was a rubbing wire at the bottom of adblue tank which cost £250 to repair which is not covered by my extended warranty this is just a ticking time bomb for anybody owning these cars this is bad design to have a harness on corner of a tank with no clips to hold it or extra protection who can you complain to it needs looking at

I have a mercedesbenz c220 bluetech 2015 had the same problem engine light came on followed by 400 miles countdown for adblue after engine will not start took to hull mercedesbenz the fault was a rubbing wire at the bottom of adblue tank which cost £250 to repair which is not covered by my extended warranty this is just a ticking time bomb for anybody owning these cars this is bad design to have a harness on corner of a tank with no clips to hold it or extra protection who can you complain to it needs looking at

O

 

[Ian68]

Hi guys.
Gonna keep this thread alive. I've just had the same issue 2017 car management light on and found the adblue issue.
Into the dealer today under extended warranty to be told a wiring issue where some rubbing had worn through causing multiple warnings on the system and not covered under warranty. I'll try an appeal through Merc uk but don't hold out much hope. The car has only done 27K so hardly hard worked.
Fortunately i haven't been charged the same as others on here -- 156 all in for a wiring repair...
Good luck all .. this is clearly a design problem.

Cheers

Ian

 

[Chimpman]

I have also had this fault recently - March 2021. Engine light came on. Contacted roadside assistance who said leave it for a week if no performance issues and it might go off. obviously concerned I had it checked with a diagnostics kit. several faults on the system. One of which was adblue. to which I suspected Nox sensors. Drove the car and a new message on the dash which read. ENGINE START NOT POSSIBLE in 500 miles. counting down. I then contacted Mercedes to have it booked in to be looked at as I have a used Merc extended warranty. Theyve had the car in today for a diagnostics of which they are saying that the fault is not covered, and due to this I have to now pay £180 diagnostics fee for diagnosing the fault, and a further £180 to repair the cable. Luckily I have a courtesy car and will be fighting the case to see if there is anything that can be done. £360 to plug the car in and receive fault information on something that is clearly a common issue. I will be challenging the decision. Especially the initial diagnostics cost considering the message on the dash about engine start not possible.

I have asked for a phone call from the technician for further details to check if the repair is something particularly difficult to carry out. I will update on any progress made.

 

[Tuercas viejas]

Guys reading this thread mirrors what goes on with MB, USA & emission related issues such as yes, NOx sensors etc.
First as an Independent shop owner we specialize in fixing hard to fix vehicles.
Euro brand cars are my best revenue earners especially in the electrical areas. (Such as communication around the car. )

Now I am a bit of an enfuziast for MB stuff, and asked once upon a time in Spain why? (by a 1938 Rolls Royce Phantom owner having fixed it on the roadside near Burgos).
I replied "Well I know you referred to the MB platforms as a poor man's Rolls Royce but I like the precision."

Unfortunately like all Euro brands the wiring harnesses are not up to scratch for longevity.
From experience MB is middle of the road, BMW isn't far behind them, and Audi VW ?? Well best not mention that !

The Japanese could teach them all about quality haresses to ISO 900 standards like Sumitomo and even Ford as good runner up.
So to your harness issue.
Yes like on this side even with a 2016 906 Sprinter we have today encountered basically the same, with an Ambo!
Unlike the UK we get 9 starts like nine lives of a cat! Meow!
This un' came in with 5 starts left !
A scan showed no Adblue activity.
Oh but we know from Ford's based tech courses that the exhaust temp sensor must come up the 174/175 Celsius to activate the Adblue system.
In our Sprinter case it was flat lined at 152c.
Change it out & the sensor comes up the magic 175 c and the Adblue system goes active !
The system gives the signal to build pressure but there is no real communication to the DEF dosing valve --There's our base issue .
Slither under the van and there it is!
A crusty harness feeding the dosing valve subjected to high heat reflection for about 4 years.( Ohmage is off the clock needs new cable plus a dosing valve probably .)
You ask yourself why doesn't MB follow Ford and armour the bloody cable against heat, its the same Bosch system, but MB doesn't.
So we make money repairing deficiencies, which is yet another reason why I like MB, a good shop revenue earner.

This repair represents about 4,5 hours of work to remedy and test.
Labor is estimated be $575.
Parts around $600
Plus tax @ 4.6 %.

This Ambo has 121,000 miles on it & way out of warranty, at 3 years or 36,000 miles.
Don't even think about asking MB for a warranty discount !!
You will get a firm NIET!

As a side bar we don't charge for diagnostics & scanner usage doing the actual repair per se.
Its covered by by included labor charges .
We do charge for the same if a DIY'r wants the info to fix it themselves, $175 is the charge.
SCN coding etc is $250.
In the end its the price of admission, & a far cry from working as an eight year old in the late 1950's in my dad's "one man showband" Vauxhall /Bedford repair shop.
Tuercas Viejas

 

[wongl]

Is there any preventative actions we can take to avoid the wiring rubbing against 'something'?

 

[Tuercas viejas]

Is there any preventative actions we can take to avoid the wiring rubbing against 'something'?

Yes we use this on wire harness rehabs and repairs on MBs
.Basically its taking a page out of Lexus /Toyota practice. (The famous Toyota Way )
High Temperature | Techflex.com
See snap wrap,
Regards
Tuercas Viejas

 

[Chimpman]

I managed to get the cost halved with the initial diagnostics cost wavered after some persistent complaining and asking to speak to managers etc. Totaling £180 for a cable repair. Still not ideal but at least sorted and I expect to a high standard.

The technician told me that the issue was something he had seen before but couldn't say if it was a common fault or not. They explained the cable would be cut back and a new section added as well as a re route.

I would advise any W205 owners of all ages to try to check this cable. which goes from the adblue tank to the SCR module and protect the cable with heatproof material or re route it.