MOT Nightmare!

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Ssun

New Member
Joined
Jan 10, 2024
Messages
5
Location
Birmingham
Car
Mercedes CLS
Hi, my CLS was MOT’d in November by a Mercedes approved garage. The MOT failed on one issue - the subframe had corroded and needed to be replaced by Mercedes which Mercedes agreed to do free of charge (this was a recall issue).

I booked my car in for the subframe repairs at the Mercedes garage and asked them to redo my MOT as I expected it would pass after the replacement part was fitted.

Instead Mercedes have told me the car has failed the MOT again as the engine failure light has come on and have given me a bill of £1000 to repair the DPF which has apparently caused the engine failure light to come on.

The car has been driven.m no more than 5 miles since the MOT in November. I don’t understand how this new issue could have arisen the second time the MOT was carried out when it wasn’t identified the first time.

I feel like I’m being conned into paying £1000 for the repairs that we’re supposedly ‘free of charge’.

I can’t take my car from the Mercedes garage as approved garages cannot replace the DPF unit so I’m stuck - either I pay £1000 or take my car home without it’s MOT.

Can anyone give me advice on what to do?
 
Get a second opinion on the Mot by booking it in with another test centre.
I've never heard of the DPF only being replaced by MB, surely any exhaust shop could do that?
 
Any decent garage can replace the DPF; it's untrue to suggest otherwise. It sounds as though the dealer you're using could be trying it on. Exactly what warning, and in what colour, has come up on the dash display?

Probably best to book another MoT test at the closest MoT tester to home, then it's technically legal to drive there for a pre-booked test, and if it fails again, just take your chances and drive it home. You might find the EML has magically cured itself on the way to the second tester...
 
Problem is the engine management light is on now so the MOT will fail no matter where I take it.

I called the approved garage that took the car to the first time and explained the situation. They said MB won’t let them replace the DPF, it has to be done by a dealership garage.

I don’t believe the DPF issue was there when I took the car to MB. Feels like they’ve done something to the car and are now making to pay for it.
 
Is there a possibility MB did the ECU emissions software update while in their workshop?
 
I don’t think so. They probably would have charged me for that too.
 
Is there a possibility MB did the ECU emissions software update while in their workshop?
Aha... I wonder... How old is the car?

Replacing a DPF is a simple enough mechanical job, though it may involve a fair bit of dismantling to get at it (I don't know, that's all), but a STAR may be needed to set it up afterwards. Any indie can do it; MB won't know anything about it, so their approval is irrelevant, unless only dealers have access to the appropriate software on STAR, which I very much doubt.

I still smell a rat...
 
Recalibrating for a new DPF using Star was simple enough, on mine at least.

But I was wondering if this CLS has the dreaded NOX sensors. I can't think how that would affect DPF recal' but I've no experience.

But it's they that need replacing often, following the emissions update. But MB saying the DPF is full contradicts that as an issue.
But becoming blocked beyond accepting a forced regen in 5 miles is a contradiction too.

Sounds like a smelly rat issue.
 
I can take the car to another garage for a second opinion but I’ll have to pay min £75 to MB for diagnostics of the engine failure light. Not happy. It’s not acceptable for MB to try and rip off their customers.

Do think I should escalate to someone more senior at MB or would I be wasting my time?
 
The car has been driven.m no more than 5 miles since the MOT in November


Take it for a decent run or get it cleaned out/forced regeneration and it’ll probably be fine.
 
You don't need to drive it to get a forced regen done just get or get someone with a decent obd scanning tool then book it in for Mot to cover yourself
 
Profile says Birmingham, take it to MSL Performance 👍
 
I called the approved garage that took the car to the first time and explained the situation. They said MB won’t let them replace the DPF, it has to be done by a dealership garage.
I’m sorry to hear of your problems.

I wouldn’t reach the conclusion that someone is trying it on just yet. It’s possible that you car has only done 5 miles since your last MOT, but the engine may have been switched on and off many times, and left idling for many hours.

To help members guide you, can you explain what you mean by “Mercedes approved garage” and “dealership garage” please? Also how far apart are they, and how far is the car from your home?
 
...the subframe had corroded and needed to be replaced by Mercedes which Mercedes agreed to do free of charge (this was a recall issue)...

Sorry not to be too interested in the bulk of the OP's post but this jumped out at me.

Ssun , do you have a copy of the safety recall letter for the free subframe replacement ? And the age and mileage ? Does it have a full MB dealership service history ?
 
It was NEVER a recall in the UK....AFAIK....as much as it should have been on safety grounds.....but I guess equally I've never heard of a Merc crashing due to this type of subframe corrosion/failure either.....so maybe they dont think its dangerous enough!!!:)
 
...the subframe had corroded and needed to be replaced by Mercedes which Mercedes agreed to do free of charge (this was a recall issue)...

Sorry not to be too interested in the bulk of the OP's post but this jumped out at me.

Ssun , do you have a copy of the safety recall letter for the free subframe replacement ? And the age and mileage ? Does it have a full MB dealership service history ?

I had mine inspected last year at MB Colindale. The tech said that if any subframe rusted from the inside out MB would do it FOC up to the age of 20 years. They ignore surface rust.

When I say FOC they often recommend/need to use new bolts which the owner pays for. And will suggest other (non-free) stuff when they're in there. Brake lines v common. Some bushes maybe.
 

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