Pre-Safe Inoperative See Owners Manual - Command line shutting down

[malyka]

Hi fellow Merc owners and experts.

Disclaimer I'm new here as I'm a newbie owner of a Merc after owning VWs. I have a lot of experience with those and diagnose, service and repair them myself. As such, I'm already working on getting myself a MB STAR Xentry kit as I've learnt that owning my own diagnostic is invaluable, especially if you can self repair.

Issue I'm getting is the error message: 'Pre Safe Inoperative See Owners Manual' shortly after starting the car, or turning on the ignition - The car radio turns on and sat flips open, then after a few seconds, no more that a minute, the message shows on the satnav display: "Command line shutting down' flickers and few times then the sat/nav flips back closed and the radio turns off. The Air con fans are limited and the seat heaters cannot be turned on.

Now the history is that I bought this car and parked for a few months because I didn't nee to use it at the time so the battery went dead. I didn't really test the car when I bought as it was from a friend(I know, schoolboy error) so I don't know if this car has always had this issue. So anyway I recharged the original battery and fitted it in and started the car ok but car kept going into this pre-safe mode.
However after driving it for a bit, the pre-safe message went away and the command line and radio/satnav flipped back up and full accessories started working again. Then randomly after a 30 mile drive they went off and never came back on. My online research lead me to this advice - Command line shuts down if the sensor detects that there's not enough battery power, in order to preserve your battery and car enters pre-safe mode. So with this I concluded that my battery was the issue as it's cranking deteriorated with each attempt, and bought a new AMG Battery and fitted it in thinking this would resolve the issue and it still hasn't worked since at all. Even after driving loads.

Following further research, also stated that the command line also shuts itself down if it detects higher voltage output that is necessary, possibly alternator voltage regulator issue. So I've taken a multimeter and carried out batter/alternator tests:

battery voltage when car off - 12.6v
battery voltage when car running - 15.20v
tested voltage from alternator to battery and all seems fine.

I'm told that the voltage when car is running should usually be between 13.4 - 14.2v thereabouts and no more. Any more indicates that the alternator voltage regulator is faulty and you could risk damaging your car battery by overcharging. But then again those figures were related to different cars and some reports say that it may vary with cars.

Please can you confirm if that's the expected charging voltage for my car or whether it's too high meaning my alternator voltage needs replacing?
Anyone else have any experience or advice on resolving this issue?

Thanks in advance.

 

[John Laidlaw]

In my 212 it’s in the higher range you’ve mentioned- 12.6 seems a little low when off and certainly high at 15.2v when running.

 

[malyka]

In my 212 it’s in the higher range you’ve mentioned- 12.6 seems a little low when off and certainly high at 15.2v when running.

Thanks for the speedy response John, I'll double check the off voltage, didn't take an exact reading for that one as it was in the expected 12v range so it might be higher.

So given your confirmation, my alternator and battery are fine and issue lies elsewhere I haven't the foggiest?

 

[John Laidlaw]

Thanks for the speedy response John, I'll double check the off voltage, didn't take an exact reading for that one as it was in the expected 12v range so it might be higher.

So given your confirmation, my alternator and battery are fine and issue lies elsewhere I haven't the foggiest?

Indeed- this Presafe thing comes up time and again, I’ve researched a bit and it can be battery voltages , sensors, seat belt buckles and various other things but rarely consistent !
Sometimes even intermittent and spurious...welcome to the whacky world of MB

 

[malyka]

Indeed- this Presafe thing comes up time and again, I’ve researched a bit and it can be battery voltages , sensors, seat belt buckles and various other things but rarely consistent !
Sometimes even intermittent and spurious...welcome to the whacky world of MB

Awesome!...Thought I was upgrading to a premium car..

So in your opinion, do you think it'll need a diagnostic reading to try trace the cause?

 

[John Laidlaw]

Awesome!...Thought I was upgrading to a premium car..

So in your opinion, do you think it'll need a diagnostic reading to try trace the cause?

Indeed sir!
My comment was a little tongue in cheek- if I didn’t like them i wouldnt be on my 5th....
They just have a few foibles more than some other brands..
So yes a diagnostic will be a good investment , third party for now but of course when you get your own Star that will go some way...

 

[alexanderfoti]

15.2volts is high.

Control modules and command will go offline when the voltage is too high as well as too low.

Where are you measuring the voltage? If at the battery terminals then I would agree with your diagnosis with the alternator regulator.

 

[malyka]

Indeed sir!
My comment was a little tongue in cheek- if I didn’t like them i wouldnt be on my 5th....
They just have a few foibles more than some other brands..
So yes a diagnostic will be a good investment , third party for now but of course when you get your own Star that will go some way...

I know you were messing, all cars come with their gripes...I'm sensing a personal pattern for my car purchases. Just after I bought my Seat, fairly new, just a 3 years old, it developed an intermittent electrical fault that Tripped fuses and immediately turned off the car. Happened a few times whilst driving, imagine how dangerous. Following various enquiries for quotes etc all they wanted was for me to draft up an open cheque (£70/hr, we can't guarantee we'll solve it, but still charge you blah blah)...so I resolved to sort it myself. I had noticed that the incidents happened turning the steering so I removed it and all seemed intact. Then I removed it's lower cover trimming above the peddles and inspected around the steering shaft..alas the cable trunking from the engine into the car was manufacture cable tied to the steering metal shaft which had a square edge. The steering overtime had braised through trunking and cables exposing wires and as it was metal caused a short circuit when contact occurred. Sorted that and never experienced issues since and still have the car. There were many other similar successes, so I'm sensing this is my first challenge on this one....

 

[malyka]

15.2volts is high.

Control modules and command will go offline when the voltage is too high as well as too low.

Where are you measuring the voltage? If at the battery terminals then I would agree with your diagnosis with the alternator regulator.

Hi Alexander, thanks for your input. Yes I measured the running voltage directly at the batteries as well as having the negative meter pin on battery and positive on alternator nut/bolt, close to regulator.

That's a bit reassuring, with that I'll get a replacement regulator as Understand that they are a common failure point. Unfortunately my model requires me to remove the alternator to replace regulator.

Might just make it my first job.
Any particular pointers I need to be aware of when removing/replacing the alternator?

 

[John Laidlaw]

Thanks for the speedy response John, I'll double check the off voltage, didn't take an exact reading for that one as it was in the expected 12v range so it might be higher.

So given your confirmation, my alternator and battery are fine and issue lies elsewhere I haven't the foggiest?

Sorry, just realised you may not have undesrstood, or I mat have not made clear it was the normal running range my 212 falls into - i.e. 13.4-14.2, mine is actually in general 13.6-14.1. So bang on currently.
As Alexander says and I mentioned 15.2 is very high. Alternator could be the culprit indeed but a diagnostic would be the safe way to know for certain