AppleFan1

Before I call MBrace with this sudden issue, I thought I would bring it up here first in case someone here knows what's going on. All of a sudden, I have no audio on radio, the CD player will not play, the voice activation will not work, the phone will not activate, etc. What in the world is going on. My wife and I went out to lunch and on the way everything was working fine. After lunch when I turned the engine on, nothing on the audio system would work. It's dead silence. The CD player is trying to load CD 6 and just keeps spinning its wheels forever. So, if anyone has an idea of what might have happened, I would appreciate it. Otherwise, I am about to call MBrace and see if they know anything (I doubt it).

AppleFan1

Well, I just talked to MBrace. They had me go out to the car and she was going to give it a hard reset. However, this time, as soon as I turned to engine on, the audio system and everything else associated with it started working immediately. The MBrace lady on the other end did nothing. She simply said that "maybe the computer needed a rest." Amazing!

texex91

It's lie going to the Dr when sick--day you go in, no symptoms. My vote is a loose wire somewhere.

AppleFan1

LOL. Exactly! I hope it doesn't happen again.

Wolfman

Sounds like a software crash.

Prior Comand systems were known to have audio cut-outs. System works but no audio whatsoever (fixed by turning Comand off and back on again) due to overdriven audio-input level, which happens easily with MP3's.

AppleFan1

When you say "fixed by turning the Command off and back on again", how do you do that. Are you talking about pushing the "on" button near the command knob? That just turns the screen off but is there something else that turns the system completely off?

whoover

Happened a couple of times in my 2006 S65. You needed to let it rest long enough for the CAN-B bus to quiesce -- about 10-20 minutes. I think it happened three times in 75,000 miles.

AppleFan1

Sorry, but I don't know what "CAN-B bus" stands for.

konigstiger

According to bulletins software is due to release 9/14 that may resolve your issue https://mbworld.org/forums/6039469-post12.html discuss with shop foreman who should check for fault codes. Check PM.

AppleFan1

Thank you! Occasionally, when I play iTunes Radio from my iPhone in the car, it sometimes does stop or goes to some music I don't even want to hear.

whoover

The CANs (controller area networks) are the computer networks that control everything in the car. The B or body bus routs signals from things like light switches, through the SAMs (signal acquisition/activation modules), which are like routers, to activate consumers (like lights). (CAN-C or chassis routs engine and transmission signals, for instance and takes priority.)

Switches don't actually switch consumers like lights and amplifiers because computer switching uses a lot less current than light switching. CANs and SAMS save hundreds of pounds of copper through the use of thinner conductors than actual switching would require.

Some error conditions are only cleared when the CAN and SAMS are rebooted. Normally this happens when you first start the car up. But the system doesn't shut down as soon as you shut the engine. It stays awake for a while to adjust the steering wheel up, etc. It also waits a while in case you want to listen to some music. When it's convinced you're really gone, the system shuts down. Only after that delay will opening the door force the systems to reboot.

A lot of odd behaviors make sense if you understand the functioning of the computer networks that control everything. For instance, dead batteries are often caused by faulty seat adjustment modules. They don't draw any current, so why should they kill the battery? It's because they put static on the bus and trick the CAN-B into thinking you're still fiddling with something. The bus never shuts down and the computer is what is actually draining the battery overnight. This is why without specialized training, diagnosing electrical faults on a Mercedes is practically impossible.

schuk

Hmm, strange... What did you eat for lunch?

AppleFan1

Wow! I never realized it was this complex with the computer systems. Thank you SO much for the detailed explanation. I now have an appreciation of how easy it is for something to go wrong.

In any case, I am now positive that what happened to my audio system yesterday was exactly as you explained. The fix is simply to wait about 10 minutes before trying it again. If it happens again, I will know what the problem is and how to fix it thanks to people like you, konigstiger, and others here on this great forum.

FutureAMGxx

What would you have to do to stop this problem from reoccurring? If for example it happens multiple times a week and you are getting really tired of it happening?

whoover

Let the dealer or a very qualified MB indy diagnose it. Like I said, it happened to me three times in 75,000 miles. But if it happens regularly some component is failing solidly enough that they'll be able to see it. It might turn out to be the COMAND head unit itself, which won't be cheap, but it could be something a lot simpler like a bad fiber optic link in the MOST ring.

(MOST is the fiber-optic ring bus that connects all the "media" devices. It's yet another complication in diagnosing COMAND problems. The amplifiers are switched on and off by CAN-B signals but fed their audio over MOST. Welcome to the modern MB.)

gapcobenz

Correction is needed here. The HU communicates with the car through the CAN BUS which is the CAN_FD system. This CAN BUS uses a flexible data rate that frees up unnecessary traffic on the BUS when certain components are not in use. The centre console audio controller and COMAND display operate on a CAN BUS that is supplied by the HU which is not conneted to the CAN_FD. The other components like AGW, amplifiers etc.. do not have connection to the car CAN BUS, these work through the HU over the fibre optic MOST system.The W222 HU is coded to the car and will not work in another vehicle. Fault finding by the MB is now easier than ever before.

whoover

I assumed the last poster was talking about a C55.

gapcobenz

No not the C55. I refer to all S- Class W222 from late 2013 to present.This is the CAN BUS system used. The new C-Class which is to be launched very soon should have the same CAN_FD BUS system but I cannot confirm this yet.

whoover

Yes, but the poster with the problem has a C55.

FutureAMGxx

Yeah, it's an '05 C55 with intermittent audio cutout. When it happens the HU works but no sound comes from the speakers and it doesn't recognize the CD changer.

gapcobenz

Yes I'm aware of the problems the poster has. I just confirmed which CAN BUS system is in the W222, after all this is a W222 forum and not for C55. The OP should post in the correct forum and maybe get help there.

FutureAMGxx

The OP does have a W222... I am experiencing an identical problem as the OP in my w203. Hence trying to find help here since I haven't anywhere else.

gapcobenz

Okay. The W203 has a different system to the W222. The US cars have a COMAND made by Alpine and possibly an external amplifier by Bose or Harman Becker Automotive systems. Also other components such as linguatronic,possibly phone,teleaid,CD changer etc.. as well are on the MOST system. I suggest you get the car to a MB dealership for diagnostics. Don't buy anything from the dealership or anywhere else. Whatever the problem it can be fixed, unless you have a component that is badly corroded by moisture.