Collision Prevention Assist Plus Inoperative

My first experience with Collision Prevention Assist was in my boss’ E-Class. It was a small red light on the dashboard which I figured out came on when I got too close to cars in front of me while driving.

Then I got an A-Class and learnt a bit more about it. It wasn’t so basic. If it thought you might not be paying attention it would beep loudly (shout in my terminology) at you to warn you that you might be about to crash.

Then I heard stories from a colleague who says he was driving on the highway, came up behind a car and all of a sudden his car automatically slammed on brakes. And this was also the fault of Collision Prevention Assistance Plus.

Now I’ve had it beep at me many times, and with my CLA it has also actually lightly engaged the brakes, but not once has it been in an instance of real danger. In my opinion. It happens most often when you’re driving behind a car and they turn off the road you’re on, slowing down considerably. I however maintain my speed because I’m driving straight. The car doesn’t know they’re turning and so warns you of your impending demise.

It is however an important safety feature, and the one time it saves you from an accident will be worth all the false-positives.

Not too unhappy am I then when I turn on my car a few weeks ago to be greeted by a yellow message saying “Collision Prevention Assist Plus Inoperative”. I check the manual and it says I must drive slowly and take the car to a dealer. This is 16h00 the day before I’m supposed to go on a 3,000km road trip. So what do I do? I find a dirt road, check the ABS and traction control are still functioning and decide to take my chances. As far as I can tell the car functioned exactly as normal besides the lack of this one function. And it was actually quite nice, because with it inoperative, it was unable to beep at me.

2015-09-09 08.16.50Eventually though, several weeks after it started warning me I took it in to the dealership. They kept it for the morning and told me they did a software update, now the message is gone, hopefully for good.

From what I’ve read on forums and discussed with other drivers, it’s not an altogether uncommon occurrence amongst CLA and GLA drivers. And in most cases a software update fixes the problem for good.

Discalimer: When I took the car in the service agent told me if they couldn’t fix it they would have to keep it overnight, as they can’t let me drive with one of the safety functions malfunctioning. Fair enough. What it does mean is that I (and you) should definitely not drive an additional 3,000 km before taking the car to be checked out.

7 thoughts on “Collision Prevention Assist Plus Inoperative

  1. Thank you. I tried calling my service agent at the dealer and after 45 minutes of getting voice mail bounces from one phone to the other I decided to try this source. Now I know what I need to do.
    Thank you.

  2. Car C300 2017, I have a message saying “Collision Prevention Assist Plus Inoperative. I cleaned sensors and windshield thought may be this is dirt that is giving me this error but unfortunately that did not worked
    I called MB dealership in Mississauga, gentleman did not show any interest and told me they are booking for appointment in 4th week or I will have to come before 4.30 that for sure I can not make due to work

    I am not sure if someone know a quick fix to this problem?

    • Hi Shad, as far as I know there is no quick fix. You have to take it in for the dealership to investigate.

  3. Hi, i had the same problem, took it to the dealership for my C220D under warranty, they did a software update which didn’t solve the problem, they did a further investigation and changed the module which seems to have kept the yellow warning out off.

  4. Hi could anyone tell me if my Mb as collision prevention assist I have a 2015 c250 and how to get it to work only had the car for two weeks.

    • Hi Peter, your car should have it. It is enabled by default, and can only be disabled for your current trip, as soon as you turn the engine off an on again, it is reactivated.
      You can confirm your car has it by going into the settings and seeing if you can disable the feature. Check your manual for instructions on how to do this.

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