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Discussion Starter · #1 ·
Two weeks ago while driving my 2016 GLA45 about 35mph at the head of a line of traffic I got the message "Collision prevention assist inoperative" and the car lost all power nearly causing an accident with the guys behind me.

The car was running but there was no response when pressing the gas. I had to stop the line of traffic, shut the car off and restart it before I could get going again.

Has this happened to anyone else. From blogs I have read this seems to be a problem that Mercedes cannot fix, and I don't understand why such a warning should incapacitate the vehicle.

I have since disabled that feature on my car, and will take my chances with my eyesight.
 

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Haven't had this problem yet on my 2016 GLA45.
 

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Same thing happened with my 2016 GLA45 on 6-23-16. Mercedes had the car towed to Fletcher Jones in Newport Beach and they are acting like they have no idea of what to do. Yes, got a loaner car, but The still have my car and this after waiting 8 1/2 months to get the car in the first place. MBZ at first said they didn't think my car had Collision Prevention which shows as Standard Equipment. What did you go through?
 

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I haven't had this issue. I've had the collision assist beep at me a number of times, warning me that it thought a collision might occur, but I never had it brake for me.
 

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Discussion Starter · #5 ·
This happened to me again last friday. I stepped on the gas to clear an intersection and got inoperative error message and the car was reduced to idle with no response from pressing the gas. Luckily I had enough momentum to clear the intersection and had to shut the engine off and restart it, after which the car operated normally.
 

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Mine (2015 GLA250) beeps several times a week, sometimes in the same location, but usually at random. I wonder if it is occasionally picking up a signal from someone's security system?
 

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Today's cars have too many systems prone to errors and failures. They are there commanded by the nanny state and we all have to endure. I much prefer driving a 30yo car - easier to maintain and control.

The 'feature' that earns the cake is this stupid tranny shifting from D (or R) to P when the driver's door is opened. Just nuts!
 

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Today's cars have too many systems prone to errors and failures. They are there commanded by the nanny state and we all have to endure. I much prefer driving a 30yo car - easier to maintain and control.

The 'feature' that earns the cake is this stupid tranny shifting from D (or R) to P when the driver's door is opened. Just nuts!
So when I shut my (seatbelt | umbrella | towel | jacket | whatever) in the door and need to bump the door at 100 miles an hour - it's going to go into Park?

That's not great.
 

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At 6 mph this "feature" shuts off. Do we trust it?!?!

Personally, I would think an easing on of the electric parking brake would make more sense.

That reminds me, for those who may not be aware, if you are moving and operate the parking brake button down by the light switch, the brake will operate gradually for use as a backup system.

On the 2017 GLA45 we just picked up, that button has moved left and down to below the light switch so that you can not see it when you are driving. I don't have an older GLA to compare it to, but I'm pretty sure it was visible before 2017.
 

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At 6 mph this "feature" shuts off. Do we trust it?!?!

Personally, I would think an easing on of the electric parking brake would make more sense.

That reminds me, for those who may not be aware, if you are moving and operate the parking brake button down by the light switch, the brake will operate gradually for use as a backup system.

On the 2017 GLA45 we just picked up, that button has moved left and down to below the light switch so that you can not see it when you are driving. I don't have an older GLA to compare it to, but I'm pretty sure it was visible before 2017.
That's all great - but - where's your Delivery thread?!? We need pictures! :D
 

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I know we're off topic, but to Wayne's question, here's a photo of a 2016:



E-brake button still down there just below the shifter
 

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At 6 mph this "feature" shuts off. Do we trust it?!?!
I think that is the case, as I have a vague recollection about opening/closing the driver's door at speed without ill effects.

Personally, I would think an easing on of the electric parking brake would make more sense.
Other brands do just that, as my recent research tells me. Still a nanny but not so intrusive or so violent.

That reminds me, for those who may not be aware, if you are moving and operate the parking brake button down by the light switch, the brake will operate gradually for use as a backup system.

On the 2017 GLA45 we just picked up, that button has moved left and down to below the light switch so that you can not see it when you are driving. I don't have an older GLA to compare it to, but I'm pretty sure it was visible before 2017.
On my 2016 GLA250 the e-brake switch is down on the left dash well below teh light switch. I would be weary about engaging it while driving. Nothing like a cable-operated e-brake.
 

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Your e-brake is where mine is then. Memory must have served me wrong from my test drive in March. I had thought the switch was to the right of the light switch.

I'm not advocating using that as a substitute to standard braking, but I had read it was considered to be a safety back up system. And since it comes on gradually, it seems like a better stopping method than forcing the transmission into park!!!

Yeah ... nannies. I'm sure the engineers have reasons for their decisions.
 

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Well add me to the list of engine stalls 2016 gla45. Happened today, good thing i wasnt on the freeway. Didnt freak out because i've learned this could happen. Although i had to stop a lane of traffic, all is well after restart. Another dealer trip yay!
 

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^Oh man. I do get the beeps occasionally and randomly from the Collision Avoidance System but it is pretty rare for them to appear out of the blue without any threats.

Usually when it beeps it is doing a good job of warning me that traffic is slowing rapidly or I am approaching closely/quickly. (Lots of traffic accordion-movement in Bay Area commutes.)

At least twice, the system did rapidly apply braking that felt similar to ABS...BRRRAP!!
Once when it thought I might hit a car turning right into a lot.
Second, when I was turning right mid-intersection and it must have thought I was going to hit the island or a car sitting to turn left next to that island.

I am dreading the day it stalls and I have to restart...with the drivers and congestion here I hope I don't get hit if this happens to me. Has not happened yet, thankful that I am reading about the potential here. Definitely hope it does not happen on a freeway to anyone!
 

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^Oh man. I do get the beeps occasionally and randomly from the Collision Avoidance System but it is pretty rare for them to appear out of the blue without any threats.

Usually when it beeps it is doing a good job of warning me that traffic is slowing rapidly or I am approaching closely/quickly. (Lots of traffic accordion-movement in Bay Area commutes.)

At least twice, the system did rapidly apply braking that felt similar to ABS...BRRRAP!!
Once when it thought I might hit a car turning right into a lot.
Second, when I was turning right mid-intersection and it must have thought I was going to hit the island or a car sitting to turn left next to that island.

I am dreading the day it stalls and I have to restart...with the drivers and congestion here I hope I don't get hit if this happens to me. Has not happened yet, thankful that I am reading about the potential here. Definitely hope it does not happen on a freeway to anyone!
Fortunately its not complete power failure, power steering and brakes still works, its just all throttle input is gone. So the cars starts coasting to zero, downshifting ect.. and especially with the nature of the DCT it slows down faster than regular auto torque converters.

Just turn the emergencies on and move over to park and hope the guys behind you is paying attention. I think its worst on city streets because you are originally not going very fast. Sounds terrible but on the freeway you have more momentum/time to move over before becoming disabled.
 

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I wonder what would happen if sensors are dirty and clean them and also see what happen by turning off the feature.
C
 

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They are two tiers using the same system. The sensor beep is a cautionary, followed by the pants-wetting panic stop. If the sensors get dirty enough, they will prompt a message in the cluster (Collision prevention assist sensors dirty) and then disable - this used to happen to me regularly driving down to Austria. If I had to guess, this problem is not within the CPA system, but rather at the link into the transmission or ECM from same. If CPA was triggering, it would clamp on the brakes and we'd have far worse than reports of loss of power, we'd have GLAs getting rear-ended. Every time my CPA has panic-stopped, I've nearly been rear-ended - and that was in heavy traffic!
 

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I need to continue to try and remember to turn off coll prev. assist as part of my get ready to drive, before I actually get going. The other day I had a room to move from my right lane into the left lane to have clear driving since neither driver was going that fast, but as you approach that car in front, it would start with the warning. Fortunately it did nothing beyond that. I had some room, but if that dang thing had turned on as I moved into the left lane there could have been an issue. LET ME DRIVE MY CAR. I know what I'm doing, not a distracted driver and need the car to leave well enough alone on this one.


E Brake on my '15 is pretty low in lower left dash area as well, but it is good to know I could push that and it would act similar to a manual e brake that you don't jam to the floor, but rather push in slowly in an emergency where you have zero brakes.
 
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