Does anyone know why when I start my car my radio does not come on. For example, the screen, does not display anything at all. someone told me it may be the amp. but some say it may be the command console. the reason why I say this because I cannot change the transmission from custom to sport? Any help

 

moved to W221 forum...

 

why not - search first ? we get hundreds of posts like yours, the forum is full of part baked unclear half diagnosed muddle ups - if people tried first, most answers are then already there - and if not it usually helps you better structure your thinking - so we have more idea of the actual fault not one little extra that is often a frustration for an owner but is usually just misleading - and if you try to reply to the longest pre existing thread - it often reminds others of things they have long forgotten or reminds them of a fix that just worked on their car last week....

as for NOTHING on screen, is it slow to the party or remaining nothing forever .... is there any radio of other source playing normally - a few clues helps us help you
if all dead and stays dead - MIGHT be another module has dies and is causing a fibre network loop to stop - many just said linguatronic is a normal failure point on these now ancient cars

here for many is something I wrote 3 years back on another forum is what is actually in the car

if you have no comprehension of how the systems works and no access to great diagnostic kit how do you think you can resolve a highly complex and unusual fault? (and note a £3k snap on scanner with latest £1k a year update can't even communicate with the W221 interior toys !!!)

Cars are not the simple things they were...

the days of a small reliable single (radio) unit rammed in a hole with a tangle of wires, one of which was 12v. and on the front you had a proper knob that turned it on and did the volume, has long gone.

In fact the world of car wiring was transformed some time after 2000 with some spooky weird beard lightweight wiring, all controlled by the CAN bus (Controller Area Network) https://en.wikipedia.org/wiki/CAN_bus

Alongside that oddity, car manu then decided what they really needed was a fast simple in car entertainment solution that was flexible and configurable to add toys on posh cars and leave them out of the cheaper ones. So they used MOST, (Media Oriented Systems Transport - a fibre optic cable link) https://en.wikipedia.org/wiki/MOST_Bus

With most cars running a hideous high voltage spark fest and a bunch of other (electrically) noisy stuff under the bonnet, placing a high end Hi Fi solution 2 foot away in a small space that's ever vanishing with more sophisticated AC systems, and with the need for it all not to jump out and hit you in the face when you crash, they moved much of it to the boot !!!

I guess much of it is a bit like posh home HiFi. If you can separate out individual components with baby low noise power supplies, each unit can have its own well shielded intricate circuitry. Thus you should get better sound quality, and you can add posh versions of these "separates" and or extra units, for additional features on higher spec cars.

Using a combination of CAN mostly for control, and MOST for the noise and picture transfer, they daisy chained all the separate bits together and wiz it to the front of the car at the speed of light.

Thus the radio is not One thing, its up to Nineteen separate components. Not counting all the speakers which is at least 7 on the std car and 14 with the big amp ... (each bold bit is a physically separate unit all but two with their own buggy outdated software)

so turn the key with the "radio" selected to an FM station, then using either the Steering wheel buttons,
user input goes via the SCM, (steering column module),
with the same info reaching the COU, (central operating unit - the Comand knob and switch pack)
they both process user requests to control the COMAND Unit, that sits in the dash under the heater buttons.
in turn that feeds the picture you see and the changes you are making on the ZAN (central display)
or a cut down version in the IC (instrument cluster - third menu to the right using left steering button arrow).
A user input like Vol adjustment, I guess goes via the Central Gateway, CGW (the CAN master controller for everything on the car),
to the AGW, audio gateway in the boot (actually called the TTU on an S class, its an Amp with integral AM FM tuner to the layman),
that in turn is connected to the ANTENNA module in the roof and the cars loud speakers.
The OCP (overhead control panel) holds a microphone (might be for the phone as well) that takes ambient noise readings,
together with vehicle speed data from the ABS,
those signals are processed in the Rear SAM and speed dependent volume control automatically adjusts source (radio) volume,
and feeds TMC or SAT NAV voice overlay from the comand back to the TTU and a view on the ZAN.

But then you can select other choices on the comand unit to do other stuff via additional optional extra modules
CTEL Phone
TV Tuner
DAB Tuner (Europe)
SIRUS Satellite Radio Tuner (USA)
Bluetooth Module
Media interface Module
Linguatronic Module, an optional idea trying to do it all inside the car - never worked - mostly for spying to get your voice on their servers processing on modern PC, cars & phones is all done in the cloud
RFK rear view camera - feeds pictures to the ZAN via Comand which has menus to control, note IC has a menu to use RFK or turn it off
GPS ANTENNA for the SAT NAV option, it goes in the back of the Comand which can hold the Map data on a harddrive inside

The Steering wheel buttons and both antenna's are the ONLY ones without their own operating system and control software !!!
All are updateable with later software releases, except the steering wheel module that can't be flashed, but a later software iteration is on a new part

Depending upon which source or feature is in use, the ANTENNA module inside a posh Shark Fin module on the roof of most modern cars can do DAB, AM, FM, PHONE and SAT NAV signals to the car

Earlier cars like w211 can have another Nav unit on the MOST in the boot)
NTG3.0 you have an orange fibre cable loop between the Comand, the TTU, the DAB, the TV, (an iPod kit is only on the CAN)
NTG3.5 you have an orange fibre cable loop between the Comand, the TTU, the DAB, the TV, the Media Interface
Linguatronic might not be on the MOST, if so its likely just confusing the CAN till its a bit odd - pull the wires and see what happens

where fitted, if one plays up they all play up