Possible brake light switch fault ML270

Andy W

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Stoke on Trent
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ML 270 cdi
My ML270 has been superb in the 21 months that I have owned it requiring only a set of pads and a new air mass meter although this aftrenoon I have the BAS/ESP, ETS, ABS and EPC warning lights up, also whilst stationary if you put your foot on the brake pedal it very slowly sinks to the floor.

I suspect it is the brake light switch for some of the fault lights but not sure about all, if I switch the ignition off it does not clear the lights on restarting. Is the car now unsafe to drive until I repair it?

Thanks guys.
 

Diesel Benz

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It isn't the brake light switch (alone) if the pedal slowly goes to the floor. In this case I would say it is unsafe to drive the car.
 

JohnnyRob

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IIRC the brake light switch problem results in BAS/ESP light and not the other lights you mention.

I'd get it looked at sharpish...
 
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Andy W

Andy W

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Thanks guys, I dont intend to drive it until I have changed the brake light switch and see if the lights are still lit after lock to lock reset, failing that a trip to my local indie will be in order, just strange it all happened this afternoon, the only thing different that happened to me was I had to slam the brakes on and when I reversed in my drive the passenger side mirror did not dip down, I had to reset the seat position to set the moirror then I noticed the warning lights.
 
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Dieselman

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The sinking pedal says there is a hydraulic problem. Are you sure it keeps sinking. What about with the engine off and servo vacuum bled away.?
 
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Andy W

Andy W

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The pedal only sinks with the engine running but sinks very slowly, take your foot off and press quickly and it stays firm but leave your foot on and it slowly sinks, engine off it is solid.

I searched google and found a reference to the pedal as occassionally being part of the brake light switch fault.

In my hand book I cant even find a reference to the EPC warning light which I had briefly, I just have the BAS/ESP, ETS & ABS now.

The only good thing to come out of it is I have now cured the stiffness and notchiness of the accelerator pedal.
 

benztech

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The brake pedal naturally sinks to the base progressively with the engine running. I think you are being a over cautious and looking for anything that could be a problem. But just to be sure check and monitor your brake fluid level in the engine bay. If you have a leak the level will drop - i highly doubt it.

What i would say is to carry out this simply test.

With the engine running turn the steering wheel lock to lock three times - turn the engine off - restart engine - have the ESP/BAS light gone. If NOT then you have a fault get it plugged into a "star" machine.

What year is your vehicle??
If the vehicle battery is 4+years old then get it tested.

What happens is there is a steering angle sensor behind the steering wheel it is very sensitive to battery voltage if your battery is on its way out then every time you start the engine the Steering angle sensor recieves an undervoltage and puts the light on the dash. You reset it by turning the steering wheel lock to lock 3 times.
 
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Andy W

Andy W

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Thanks for that benztech, very interesting.

Right I decided to have a another check, started the engine and the BAS/ESP, ETS & ABS lights still on, tried the lock to lock reset again, no difference, I had already checked the brake fluid and checked for vacuum leaks (clutching at straws I know) so I decided to take it along the road to see if the doors auto locked at 5 mph, pulled off, the doors locked and all the warning lights went out!

I am still going to get a new brake light switch for my own piece of mind.

Incidentally the accelerator pedal is working great now with no stickyness etc which the ML is famous for, I have also got round to fitting my alloy pedal covers, the accelerator rubber had to be completely modified as one is not available for the type of pedal fitted to the ML.

Thanks for all your help guys and I will keep you informed if the problems happen again.
 

Diesel Benz

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The brake pedal naturally sinks to the base progressively with the engine running. I think you are being a over cautious and looking for anything that could be a problem. But just to be sure check and monitor your brake fluid level in the engine bay. If you have a leak the level will drop - i highly doubt it.
If my brake pedal sinks slowly to the floor irrespectively if the engine is running or not, I would start finding a malfunction. How about others?
 
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Andy W

Andy W

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If my brake pedal sinks slowly to the floor irrespectively if the engine is running or not, I would start finding a malfunction. How about others?
I know what you mean but it only happened since the warning lights came on, all very, very odd, I shall proceed with caution .......... beleive me:eek:
 
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Andy W

Andy W

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Picked up a new switch this afternoon from the dealers, £10.00 + VAT, fitted it, everything seems ok, will see how it goes over the next couple of weeks, thanks for the help and info guys.
 

benztech

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If my brake pedal sinks slowly to the floor irrespectively if the engine is running or not, I would start finding a malfunction. How about others?
Keep your foot on the brake on any mercs 98 onwards and the pedal will creep to the floor gradually its how the brake servo works.

I have been a master benz tech for 15-16 years, i understand the product and systems very well, i do it day in day out all day long.

If you need any genuine advice about anything technical

Im here to help!:) :) :)

Im not a guesser:) :) :)
 

Diesel Benz

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Keep your foot on the brake on any mercs 98 onwards and the pedal will creep to the floor gradually its how the brake servo works.

I have been a master benz tech for 15-16 years, i understand the product and systems very well, i do it day in day out all day long.

If you need any genuine advice about anything technical

Im here to help!:) :) :)

Im not a guesser:) :) :)
I don't think I have called anybody a guesser (if I had, I would apologise but so far I don't). But I'm not satisfied for an answer from a person who has been a master tech for "only" 16 years, I'd prefer "a guided tour" because you certainly are able to give that. I'm here to learn, not to get convinced, I'm not expecting anyone taking my word for a truth, at least if I cannot backup it with easy to understand references etc.

I believe I've had 4 new mercs from 98 onwards and I have not noticed the behaviour. Do you mean the pedal sinks all the way to the bottom? What happens when it is at the bottom, I hope it is still braking at full power if I wanted so. How long should I stay standing on the pedal to make it reach the floor, I want to try it on my cars? Note that one of them has SBC brakes.
 

RiaanS14Drifter

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Dec 26, 2011
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Ml 270 cdi
Hi Guys, maybe you can assist me, my 270 Cdi Ml (04) model turned 205 000km today on the highway. At that exact moment the EPC light came on, engine cut and that was it. Had to pick the vehicle up on a trailer and would like find out about possible faults. The engin turns when I trun the ignition now but no start.

Any assistance will be highly appreciated.

Regards Riaan
 

Daisydog

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Oct 18, 2015
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20
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Ml270
Question for you ! My esp/bas light is on and showing as steering angle sensor on diagnostic machine . It's a 2001 ml270 . Mercedes benz say it's all one unit in steering column part is £650 !! But I have seen sensors on ebay separate to column so this doesn't ring true ? Some as little as £50 secondhand . Anyone have any experience changing this sensor on an ml270 ? Tips much appreciated
 

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