C5 Mk1 computer powering down

[bighairybloke]

My C5 clock, central locking, etc powers down after about five mins after locking the does using the fob.

Come back within 5 mins and I can use the fob to open the doors and the clock retains its time but after that the fob won't work and the clock looses its time. I have checked all the fuses in the car passenger footwell and even replaced the battery with a brand new one(varta).

It's irritating more than anything, any ideas?

Cheers

Steve

[GiveMeABreak]

When you replaced the battery, did you follow the BSI reset procedure? If not follow this and don't skip any parts:

• Put the driver's window down, lift the bonnet and ensure all equipment is switched off.
• Ensure all doors are closed and remove key from the ignition.
• Wait for 3 minutes, disconnect the vehicle battery and wait at least a minute.
• Reconnect the vehicle battery, wait a further minute (do not open doors).
• Switch on the side lights through the driver's window.
• Switch on the ignition and check system's functionality.
• Hold lock button on key down for 10 seconds.
• Remove key open & close door test central locking system.
• Start the engine and complete the system's check.
• Failure to follow this procedure could result in incorrect operation of many BSI related items.

You have to remember these cars have a myriad of Electronic Control Units and like computers they need to be powered on and off properly - disconnecting the power (or the car battery in this case) without allowing them to shut down can cause gremlins. Try the above and hopefully it will cure your gremlins.

[bighairybloke]

Yes I believe I did, but I will do it again tomorrow and let you know how I get on.

Cheers

Steve

[wheeler]

Do you have an aftermarket stereo fitted ? This normally happens when an aftermarket stereo has been incorrectly fitted.

[bighairybloke]

No, it's the The original radio.

Cheers

Steve

[wheeler]

Does the radio also loose its pre set stations after the 5 mins ? If so it sounds like the comfort VAN network has lost its permanent power supply. When the BSI 'wakes up' the VAN+ supply is powered & it stays awake till the BSI shuts down (normally around 3 minutes after switch off) hence the reason it is all still working until the BSI goes to sleep. We really need the wiring diagram for the multi function display to see where it gets its permanent supply from.
You say you checked all the fuses inside the car ? How did you check them ? Did you check both sides of each fuse with a meter or test lamp ?
Is the shunt fuse (the one marked SH) in place in the fusebox/BSI ?

[bighairybloke]

Thanks wheeler. That perfectly describes my symptoms! BSi start up prop didn't resolve issue. I pulled each fuse and check them with a multimeter.

Will check them again today, are there any fuses anywhere else?

Steve

[GiveMeABreak]

Thanks wheeler. That perfectly describes my symptoms! BSi start up prop didn't resolve issue. I pulled each fuse and check them with a multimeter.
Will check them again today, are there any fuses anywhere else?
Steve

I can probably help with a wiring diagram - post up your VIN so I can pull up the right one.

[bighairybloke]

Hi, I have double checked the fuses, all are good. I have even borrowed my friends new car battery to see if there will be any difference and there wasn't.
Still no radio even when running, and central locking not working five mins after locking with fob.

Is the vin the number displayed through the windscreen?

Cheers

Steve

[Hell Razor5543]

Yes, it is, amongst other places.

[bighairybloke]

VF7**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Well here's the wiring section for the Instrument Panel, Multifunction Screen and BSI.
7215 is your Mutlifunction Display
9004A is the Comfort VAN Data Bus
9005A is the Comfort VAN data Bus B
B7215 is the Battery +
M7215 is the Earth

The 4 outer right wires continue up from the bottom to the top diagram so you can see where they terminate at the 10 way black connector at the BSI (10V NR)

[bighairybloke]

Thanks Marc. Wow, where to start. I am not familiar with this type of wiring diagram. Looks like I need to verify 12+ at this 10V NR? Where is it located? And find where f11 is in the BSI box maybe? Are the BSi connections marked?

Thanks for the help.

Cheers

Steve

[GiveMeABreak]

The wires should be marked with the code Steve - i.e. B7215 from the multifunction display back to the BSI where the fuse F11 is in the engine bay. I would also check the earthing points too.

[bighairybloke]

Ok, first I checked the fuse 11 it is fine, there is no corrosion anywhere. Also, the earths all are clean and secure.

I also pulled plug Noir to check there was 12v on pins 1 & 8 and there is none. I suspect there is something amiss here? There should be voltage here to feed the radio and computer etc I believe.

The box with all the fuses and where the black grey and green plugs go in, is there circuitry below that could be faulty? Or a relay?

Cheers

Steve