I have now had experienced this warning twice; once when I was pulling out of our development and just tonight while driving at highway speed. Tonight it felt like there was no power (scary) and I had to pull over ASAP. Then I restarted the vehicle and everything worked again.
My car is always clean so a dirty sensor is not the cause. I'm calling the dealer Monday to see if they can help. Here is what it says in the manual:


Vehicles with the Active Driving Assistance package:


PRE-SAFE® Brake is temporarily inoperative. Possible causes are:

- function is impaired due to heavy rain or snow.

- the sensors in the radiator grill and the bumper are dirty.

- the radar sensor system is temporarily inoperative, e.g. due to
electromagnetic radiation emitted by nearby TV or radio

- stations or other sources of electromagnetic radiation.

- the system is outside the operating temperature range.

- the on-board voltage is too low.


When the causes stated above no longer apply, the display message disappears.

PRE-SAFE® Brake is operational again.


If the display message does not disappear:

- Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.

- Secure the vehicle against rolling away (Y page 183).

- Clean the sensors in the radiator grill and the bumper

- Restart the engine.

 

though the sensors may appear clean cleaning them can resolve the issue- i had this once after i detailed mine and trust me they were NOT dirty-- but i then figured out the wax on the sensors threw it off-- extra rubbing/cleaning the sensors was what I had to do..

 

The sensor doesn't appear to be at all dirty or have any residue on it but I'll give it try. As I mentioned, the vehicle is rarely ever dirty (I'm very fussy that way) but if residue from washing it is the cause, the sensor is much too sensitive (IMO).

Thanks for the tip sraza. I'll be talking to the service department on Monday to get their take on it and post any results or findings.

 

] Tonight it felt like there was no power (scary) and I had to pull over ASAP. Then I restarted the vehicle and everything worked again.
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This is the part that would worry me and definitely require a call to MB.....are you saying the engine was not responding?

The other aspects would most likely be sensor realted, but tied in with this "no power" sensation, it could be a program issue.

 

Yes, the engine was not responding normally, I would guess I only had about 30% of normal power to work with. I was trapped in the passing lane beside an 18-wheeler and had no power to pass the truck. I was flooring it and could not get around him. So after the truck passed me on the inside lane, I made it to the side of the road where I was able to stop and restart the car.

You wouldn't think MB would design the system to react in this way due to a dirty sensor! But it is a complex system so who knows? Hopefully the service department can provide some answers.

 

That sounds like a major engine control module failure and therefore should show a code when they look at the system. I remember reading somewhere about the vehicle having a "limp home mode" in which there is "reduced engine power"....what circumstances and where I read that, I can't recall but in any case the computer should show the fault code.

 

The GL is going into the shop this Thursday for a look. I'll post whatever they find.

 

Update: The dealer had the car all day Thursday and half a day Friday but could not find the cause of the power loss. Their head technician was on vacation this week so they scheduled the car to be brought back in next Wednesday for more diagnostic analysis. I hope they can figure out what happened (twice). They agree with me that it should never lose power to the point of being unsafe on the road. The system was almost acting like a collision was about to happen.

 

The service department just called to tell me that after having my GL for 4 days they were unable to diagnose and resolve the issue. They said there were almost no stored error codes. They sent a diagnostic report to MB corporate head quarters in New Jersey and after a day of looking it over they replied that they could not offer any additional suggestions for the technician. So they are returning the car and want me to drive it until it happens again and then call them. Not the outcome I was hoping for.

 

I also saw the same warning when I was nearing 10,000 miles. I was able to take a print shot of the error and show to the service adviser. Initially the adviser was worried about some major hardware failure and wanted to keep the car for a couple of days for running diagnostics. After completing the Schedule A service, the technician ran some test and were unable to get any error codes. They let me have my car...so far no issues in the last few days.

 

No error codes?? That is definitely frustrating.....If you have a cell phone with a camera....take a picture of the screen the next time it happens and/or it its feasible....pull over, leave the engine running and do an mbrace call to roadside assistance. Leave the engine running for them to see it when they arrive. Not the easiest of solutions but I know that corporate MB is pretty tough on what the service techs are allowed to do if they cannot physically see evidence of the issue. To which I have always wanted to say...."you think I would make this up in order that I can make life miserable for myself?" Good luck and keep us posted.....

 

We're heading to Myrtle Beach next week so if it happens again I'll use mBrace to hopefully upload some diagnostics.

Thanks for the tip Brad.

 

I had a similar message, intermittently, "distronic plus inactive." after a couple, "no error codes found' from the dealer, I took it in while it desplayed the fault and had them scan it WITHOUT restarting the vehicle so that they could scan the vehicle with the fault active. They found a faulty battery sensor.

Is this the problem/error what caused mercedes to allow you to trade your vehicle in for the 2014 GL550?

 

Our issue involve a serious drop in power when this condition occurred, making the vehicle undrivable. Mercedes agreed with us that this condition was unsafe. They are still going to work on the issue but we no longer have to be without our car while they try to figure it out.

 

OK guys heres an update that could help out but this is a little more common the the ML166. There has been some wiring issues near the high pressure pump. There are some sharp edges and the wiring harness can rub through. I have seen the CAN wires rub through and this will cause pre safe lights and also check engine light and other faults. You may also have a no power issue that some have experienced. Some times you will not have any fault codes for the check engine light and that is why it can be hard to diagnose. When this CAN wire shorts out, this can affect all modules on that CAN circuit including engine, trans, ISM, presafe etc. Let me know if you have any specific questions. I am not on here a lot so I will try to help out asap

 

mstrbenztech: I passed this onto the local MB dealer as we already traded the 13 GL550 for a new 14 GL550. Thanks.

 

I must say that if mb allowed a trade with only your verbal description, that is pretty nice and responsible of them. Hope that it didn't adversely affect you in the financial dept.

 

My A 200 just stops without power and gives me the above messages. It is very very dangerous and NOT what is expected from a Mercedes. I believe other people had the same problem. A software upgrade does not work and the dealer battles to find a solution. Better to sell the car and move away from Mercedes? Head office suggests you contact the dealer and the dealer does not know! In the mean time I drive a very unsafe car.

 

my wife's CLA250 did this a couple of times. the car was going into limp mode. same thing as here: she would kill the engine and crank it back up - no more issues. i brought it in and had techs look at it. the wiring harness, because of location, was being worn through. they replaced the entire computer module and harness and have had no issues since.

i have also had similar messages pop up on my E350 saying 'distronic plus inactive, pre-safe limited, blind spot assist unavailable, etc' but that was always due to a torrential downpour. once the weather cleared up some, systems came back online. i never had my car go into limp mode from it.

what you're dealing with, from my experience, sounds to be a harness connection/module issue. if that's the case, it may not store the codes as it's not exactly an error WITHIN the computer or engine system, but more of a connection issue, somewhat like a short. i would ask the techs to look at the entire harness and wires to see if something is pinched, cut, eroded, etc.

good luck!

 

I was driving at speed with autonomous cruise control (Distronic Plus) in my 2014 GL350. Minor distraction as the display popped up all the error messages about distronic plus unavailable, pre-safe unavailable, blind spot assist unavailable, lane keeping unavailable, etc, etc... applied accelerator to maintain speed now cruise control was out. Noticed stopped traffic ahead, applied brake as quickly as possible (no pre-safe brake). Couldn't stop fast enough, and the car is 3 tons, so... caused a 3 car accident. Thanks Mercedes!

This is the second time I've had all of these features fail. From memory the previous time was in heavy rain and I wasn't that surprised. But this was a clear day.

 

My 2014 E350 had the occasional instance where these systems went inactive. Most of the time it was in terrible weather where the radars and sensors couldn't distinguish anything because of the rain. However, all other safety systems (ABS, adaptive braking, brake priming, etc) are still functional. The systems are not to make the vehicle autonomous and even MB states that these systems are not to be a replacement for human interaction and intervention. You even stated that you applied more throttle and pressed the accelerator. I don't think Mercedes had anything to do with your accident. It was driver error. No offense...just stating it like I see it.

 

I had this come up a few times in the past couple of days. Each time it was when I went through thundershowers. Cleared up after moving out of the weather. I wouldn't trust an automated system in those conditions anyway.

 

Hi all

Just bringing this subject back up as I have this issue with my 2013 GL63 AMG.

I only get the pre safe and blind spot assist error messages but know that the distronic and park sensors are also off at the moment.

Have restarted several times, no change, comes on a few seconds after start up.

It will be going in but anyone have any ideas, seems strange that my par sensors are off when reversing if the front radar can be the cause of the pre safe message?

Thanks

Carl

 

Hi All
Brand new 2017 E43 AMG...625 miles!!!!...seriously.
Same problem: "PRE-SAFE Functions limited" warning came up on the screen. Stop/restarted engine but error still present.
Car is spotless.
Trip to dealer tomorrow morning....what a drag.
Will keep you posted.

 

This actually happened to me about 3 days after getting the 13 GL550. Dealer blamed it on the radar detector and asked me to drive without it on. Had to go in and out of service about 3 times. The final time it came back on right after I had just left the dealer and it turned out to be the soft close module in the driver's door causing the issue. They replaced it and haven't seen it on. My escort 9500 has been plugged in the whole time since then too.