E212 Harmon K system

[W212Chris]

Happy New Year to all. Hoping 2024 is both kind and gentle to you all..

I am having issues with my COMAND system in that I have no sound. Having replaced the screen I can now see the Mercedes Logo on bootup etc but am unable to access the Sys area ?
My DTC check indicate there being an issue with the Head Unit as I cant communicate with it.
The car has the Harmon K system fitted, so I have found what i beleive to the AMP in the rear boot. My question is, would this replace the AGW or act as the AGW, or is there another unit within the car ?

Chris

 

[Alfie]

Happy New Year to all. Hoping 2024 is both kind and gentle to you all..

I am having issues with my COMAND system in that I have no sound. Having replaced the screen I can now see the Mercedes Logo on bootup etc but am unable to access the Sys area ?
My DTC check indicate there being an issue with the Head Unit as I cant communicate with it.
The car has the Harmon K system fitted, so I have found what i beleive to the AMP in the rear boot. My question is, would this replace the AGW or act as the AGW, or is there another unit within the car ?

Chris

I believe we may have communicated via email already.

The HK amp is the 'gateway' for the sound. Unlike earlier E classes though its not an AGW as such. It doesn't house the tuner for instance.

If you are getting no sound at all but the screen is functioning then you have a problem with the fibre loop and/or one of the devices on it. If you are getting no functionality on the screen then its most likely the head unit itself.

You should pop down to Lightwater and see us ;-)

 

[W212Chris]

I believe we may have communicated via email already.

The HK amp is the 'gateway' for the sound. Unlike earlier E classes though its not an AGW as such. It doesn't house the tuner for instance.

If you are getting no sound at all but the screen is functioning then you have a problem with the fibre loop and/or one of the devices on it. If you are getting no functionality on the screen then its most likely the head unit itself.

You should pop down to Lightwater and see us ;-)

Morning buddy,

you have been kind in emailing me and having taken your tips/advice i have tried to follow through the process but have come to a grinding halt.

Sadly, although I would love to pop down to you guys, it is just that bit too far.. But thank you again.

Chris

 

[W212Chris]

So I am thinking that the MOST malfunction will impact upon the two other faults ?

HU(Head Unit Control Unit) ( 3 DTCs )

D019

MOST communication has a malfunction (ring break at position 2).

C255

Communication with the central display has a malfunction.

D185

Communication with the control panel 'Head unit' has a malfunction

 

[Alfie]

So I am thinking that the MOST malfunction will impact upon the two other faults ?

HU(Head Unit Control Unit) ( 3 DTCs )

D019

MOST communication has a malfunction (ring break at position 2).

C255

Communication with the central display has a malfunction.

D185

Communication with the control panel 'Head unit' has a malfunction

Yep.

Need to see whats at position 2 on the fibre ring. the diagnostics should tell you that.

 

[W212Chris]

The latest test with Autel, shows the following.

I think it is definitely the HU that has gone.

 

[W212Chris]

At last some progress. I lifted the carpets again and checked the connections. Strangely now when I loop the fibre after the 1st connection the sound works. But I do not have Bluetooth or the ability to use the centre consol knob. I am now of the opinion that the fault must be from the FO in the passenger footwell back to the HU.
Close to being Right ?