2008 W221 Dashboard Possessed!!

[NeterKhertet]

Hi All,
I have a 2008 Mercedes S-Class S320CDI L (W221 - Pre-facelift), Its unfortunately been off the road for a while, and I'm in the process of reconditioning it and getting her back up and running, I have a couple of issues, that I wonder if I could get some advice on, from any knowledgeable parties:

01) I know my amplifier is going to need a repair/refurb - I intermittently get no sound from it and when that happens you cant select radio stations or anything like that, that I know about.

02) I've recharged both batteries (although they might need replacing) so that is a possibility (i.e. not enough power)

03) When trying to start the engine turns over but doesn't catch, I cannot hear the fuel pump (in the fuel tank running) I have removed and tested it so I know it works, I've also checked the fuses and none are blown, although there was some white oxidisation on/around the contacts for the fuse in the main fuse compartment that resides under the ECU under the bonnet, I've got pulled the relay to test that but haven't done it yet, Is there anything else that could stop the fuel pump running?

04) This is the most interesting and worrying one, the dashboard or COMMAND system seems to restart itself every few minutes, its not just the media display but the electronic dashboard as well it all restarts seemingly at random, I'm not quite sure where/what to check, could it be related to the amplifier? Or could it be the ECU (could it have got moisture in it somehow? - I not that the under the bonnet (above the main fuse box) the outer screw nearest the wing has quite a lot of surface rust on it, that would indicate it has got wet, but the ECU itself has none.

These are the error codes I currently have:
P2506 - ECM/PCM Power Input
U0400 - Invalid Data Received
P2506 - ECM/PCM Power Input (again)
U0400 - Invalid Data Received (again)

I do need to clear and rerun those again as that was before I charged the batteries, and it just had a booster pack on the "auxiliary or starter" battery under the bonnet -
Incidentally I rang a couple of places and they all advised me to put the booster pack on the battery in the boot (ie the massive one) in order to jump start the car, but if I do this the starter won't turn at all, it would appear that the smaller battery under the bonnet is for starting the car, and the larger battery in the boot behind the seats is for ALL the electrics and gadgetry, but they both need to have proper voltage, so neither one is trying to power the whole care by itself - its possible my larger battery doesnt have enough power in it even after charging for two days.

Any advice or suggestions as to what to look at next would be greatly appreciated.

 

[Richard Moakes]

I would start with two new batteries, it will eliminate a potential cause of many issues.

The battery in the boot supports the majority of the electronics and the battery under the hood is purely for starting the engine. They can be joined together by the battery control module to assist with starting, but that’s automatic depending on voltages etc.

 

[NeterKhertet]

I would start with two new batteries, it will eliminate a potential cause of many issues.

The battery in the boot supports the majority of the electronics and the battery under the hood is purely for starting the engine. They can be joined together by the battery control module to assist with starting, but that’s automatic depending on voltages etc.

Thanks Richard,

Yes that helped a lot, guess pulling the two batteries I had and putting them on charge for several days wasn't good enough, two new batteries and the tiniest squirt of easy start you could imagine and the lady fired right up!