£700 wasted still trying to diagnose electrical gremlins- any help appreciated

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GT56

New Member
Joined
Jun 14, 2022
Messages
2
Location
kent
Car
w204 c180
Dear all

My w204 m274 C180 is causing me endless headaches

On (almost) every time the car has been started up and then driven off, as soon as it reaches approx 20 mph:
- All dash lights flash
- power steering cuts out for a few seconds
- car thinks handbrake is still on and makes assoc beeping noises for a few seconds
- doors are locked but car tries to relock them
- headlights flash on and off rapidly for a few seconds

See this youtube video- pretty much exactly what happens:
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skip to 1:30 to see warning lights

the youtube video's owner says their issue was due to dodgy speed sensor but I cannot believe that 2 mercedes main dealers with diagnostic software would not be able to spot this if this was the issue.


I've taken it to my local garage and 2 mercedes main dealers- initial merc main dealer assured me that a 'software update' would fix it and charged me £400 for the privilege, before the same thing happened again straight afterwards when I picked it up and refused to refund, telling me ' the computer system told [them] it needed doing. Then charged for further time to investigate.
They then wanted to replace the start stop battery first but said it could also be the SAM and suggested that I would have to cough up £1000 for them to do the battery. I swiftly told them to **** off as I had no idea what the start stop battery would have to do with power steering cutting and the lights flashing + they already ripped me off with a BS software update.

The next merc main dealer took the car for a diagnostic check and said they needed to book it in for at least another couple more hours of diagnostics - overvoltage potentially due to bad ESP module. Interestingly no mention of the stop-start battery or front SAM ???

Both main dealers have had the car plugged into their diagnostic software with no real outcome

I'm sick and tired of wasting yet more money on a 10 year old base spec merc but won't sell it yet until this is sorted as next owner shouldn't have to deal with this BS.


I have learnt my lesson about owning an older, out of warranty merc



Any thoughts on the cause?
 
Welcome aboard,in the video,why is the guy driving with the parking brake symbol on the dash,with all these electrical problems you have to follow some sort of trail,first must be the battery it's connections positive ,negative and earths,you say like the video you get to 20 mph and things happen,check out the wheel speed sensors,,the electric hand brake can give problems,maybe with the engine running give the wiring loom in the engine bay a decent tugging to see if you do not have a short in it ,with electrical problems like this instead of using a expensive main dealer maybe the route to go is a good auto electrian,they need to remove all the things from running that are not needed to start the car and then add them back to see if the problem happens
 
First thing I would do is drive the car with a diagnostic machine showing live data from the ABS module, and see what the wheel speed sensors are reading. If it happens at 20mph everytime it almost certainly has its root in those readings
 
years ago i had a similar fault with a BMW..it was a wheel spin relay....don't if that's any help
 
As Jobsworth has said, it needs a Mastertech plugging in and running with the car to attain live data. Welcome along BTW. 😎
 
Dear all

My w204 m274 C180 is causing me endless headaches

On (almost) every time the car has been started up and then driven off, as soon as it reaches approx 20 mph:
- All dash lights flash
- power steering cuts out for a few seconds
- car thinks handbrake is still on and makes assoc beeping noises for a few seconds
- doors are locked but car tries to relock them
- headlights flash on and off rapidly for a few seconds

See this youtube video- pretty much exactly what happens:
To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.
skip to 1:30 to see warning lights

the youtube video's owner says their issue was due to dodgy speed sensor but I cannot believe that 2 mercedes main dealers with diagnostic software would not be able to spot this if this was the issue.


I've taken it to my local garage and 2 mercedes main dealers- initial merc main dealer assured me that a 'software update' would fix it and charged me £400 for the privilege, before the same thing happened again straight afterwards when I picked it up and refused to refund, telling me ' the computer system told [them] it needed doing. Then charged for further time to investigate.
They then wanted to replace the start stop battery first but said it could also be the SAM and suggested that I would have to cough up £1000 for them to do the battery. I swiftly told them to **** off as I had no idea what the start stop battery would have to do with power steering cutting and the lights flashing + they already ripped me off with a BS software update.

The next merc main dealer took the car for a diagnostic check and said they needed to book it in for at least another couple more hours of diagnostics - overvoltage potentially due to bad ESP module. Interestingly no mention of the stop-start battery or front SAM ???

Both main dealers have had the car plugged into their diagnostic software with no real outcome

I'm sick and tired of wasting yet more money on a 10 year old base spec merc but won't sell it yet until this is sorted as next owner shouldn't have to deal with this BS.


I have learnt my lesson about owning an older, out of warranty merc



Any thoughts on the cause?
Alex @alexanderfoti is on the forum , who runs AMF Mercedes near Tonbridge , Kent (MB specialist) if that helps you
 
You get a lot of strange problems when the main battery starts to play up, make sure it’s fully charged.
You also get lots of faults showing when an ABS wheel sensor fails, typically over 20 mph. Mine went recently and I had gearbox faults, abs, power steering plus other dashboard lights come on. Checking the wheel sensor with my Icarsoft MB revealed no output from left wheel sensor, this was fixed and all other faults disappeared.
When the fault was first cleared it would previously come on again around 20 mph.
 
From my own recent experience (and self inflicted fault) I can tell you that 20Mph is a trigger for wheel speed sensors etc. as that is exactly when mine would go into fault too.
Does it have fuses/relays for ABS/Traction that you can pull and disable that system? If so I'd be keen to try that and see if that narrows the field somewhat.

One idea: If as you say you've learned a lesson about out of warranty stuff, shop it in at the dealer that charged you for a software update and make it their issue. :cool:

If you're near Maidstone, I'm happy to try to help with my diagnostic and see if we can read live data from the wheel sensors etc.
 
You can switch the abs and traction control off completely to test. Turn the ignition to position 1, then press the trip reset button quickly three times. The hidden engineering menu will appear. Scroll through until you find where you can switch dyno mode on. That disables ABS and ESP completely. Disclaimer - at your own risk. Obviously no assistance if you need it.
 
Yep wheel speed sensor almost certainly. I had the C180 coupe previously but was a 2015 and had the same issue.

As you say its almost 10 years old so why do you keep taking it to the main dealer? A Merc specialist would have probably sorted it out in one go and charged half the price
 
Thank you all for your kind messages

As an update; taken to main dealer (i know; more self-flagellation) and diagnosed as failing ESP/ABS control module. £1700 replacement cost. They are '95% sure' that this will fix the issues - they have found overvoltage codes localised to that module.
 
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I would insist on dinner first if they are going to treat me like that! Have you tried an indie MB specialist, they tend to be a bit more pragmatic especially with older cars although 10 is not old in my book.
 
Have you had the charging voltage levels checked?
Could be overcharging.
 
Thank you all for your kind messages

As an update; taken to main dealer (i know; more self-flagellation) and diagnosed as failing ESP/ABS control module. £1700 replacement cost. They are '95% sure' that this will fix the issues - they have found overvoltage codes localised to that module.
WTF!?!?!😳😳😳
 
I would find a good independent Mercedes engineer and let them have a look… the 95% certain for £1700 would put me off. Quite possibly only a speed sensor so alot of change out of that..
 

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