Active bonnet management mafdunction w212

[ozthecoz]

Just had the active bonnet management function warning flash up on my dash board.
I've had no bumps or crashes and it came on whilst driving.
Can anybody shed any light on this ? Is it safe to drive ?
Car is a w212 220 Cdi e class.

Thanks
Dave

 

[ozthecoz]

Interestingly enough the message cancelled after approx 10 miles of driving and is not stored in the service / alert part if the menu

Hmmmmm ?

 

[ozthecoz]

And it's back again.

Any comments ?

 

[grober]

The active bonnet system comprises three impact sensors in the front section of the car and special bonnet hinges which are pretensioned and locked into place with strong springs. The sensors signal a collision with a pedestrian to the electronic control unit, which immediately activates two electromagnets in the hinges. These electromagnets release the lock, allowing the spring action to raise the rear of the bonnet by 50 mm. This whole process takes only a fraction of a second.

I would suspect some form of intermittent electrical glitch causing a fault to be registered. Quite possibly a known "gremlin" your MB dealer should be able to assist may------- just require a minor adjustment.


edit :---there is a reset procedure evidently------- http://www4.mercedes-benz.com/manual-cars/ba/cars/c204/en/overview/motorraum9.html

 

[ozthecoz]

Shall have a look at that in the morn though I think an electrical gremlin sounds about right as the warning went again pretty soon after and snt showing.

 

[gmahadew]

Hi Any News about this? i've found a reset procedure you can DIY, pretty easy but did not work for me .. so hoping you guys have some new insights

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[Chernooba]

The active bonnet system comprises three impact sensors in the front section of the car and special bonnet hinges which are pretensioned and locked into place with strong springs. The sensors signal a collision with a pedestrian to the electronic control unit, which immediately activates two electromagnets in the hinges. These electromagnets release the lock, allowing the spring action to raise the rear of the bonnet by 50 mm. This whole process takes only a fraction of a second.

I would suspect some form of intermittent electrical glitch causing a fault to be registered. Quite possibly a known "gremlin" your MB dealer should be able to assist may------- just require a minor adjustment.


edit :---there is a reset procedure evidently------- C-Class Coupé - Interactive Owner's Manual - [Overview | Active bonnet (pedestrian protection) ]

Hi, I have a e220 cab 2012 and I am experiencing this warning message coming and going randomly since I left the car out in very hard frost (Scotland). I also have not been in a bump and car is pristine. I see that when it refers you to the manual, it explains about an actual activation, not a malfunction, which is annoying. Anyway can anyone let me know if this was a sensor issue or something else before I get ripped off by my local mb dealer??
If anyone can can you email me on [email protected]

Thanks

 

[grober]

I believe the first active bonnet devices were pyrotechnically activated making them one use only like airbags. Later ones are spring loaded and can be reset by the owner. You might have to get the car on MB Star to see if there are any fault codes stored- but anecdotal reports tell of no code stored with owners experiencing similar warnings. If theres no codes to be actioned I'm guessing that they may recommend replacing the activating units if that's a known fix?
Active Bonnet | Mercedes 500SEC.com

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further searching the net seems to focus on the active bonnet control system requiring the bonnet to be fully closed and the bonnet release handle mechanism being fully reset. One assumes that if the active bonnet system senses the bonnet is not properly closed [ false intermittant signal]--the bonnet catches have limit switch/es to warn if its its closed properly and these can get sticky if not lubricated properly triggering false bonnet open warnings- there was a thread on this recently] -- then this might register as a fault- adjusting or lubricating the bonnet catches may help?
Bonnet open warning

 

[richard]

Yes, Grober is correct. Original were pyrotechic and you had to replace them. We did a couple of them when they first came out because some MB dealers didn't know what to do. (and both were on cars with trivial impact) The part started off very expensive but then they decreased the price I seem to recall.

I guess customers got bored of paying for that, so they went electromagnet/spring loaded instead.

Richard