Afternoon,
Bit of a head scratch, which I may have found the cause, after much searching etc, not found anything specifically the same, so just after either, i'm in the right place to look / replace part or I'm way off!

So 2004 D2 TD5 has a strange fault where it is completely dead sometimes (swear at it, open close doors, wait a while and it becomes alive again), as in if you disconnect the battery, nothing works not even the hazard lights.
I had a thought the BCU could be the issues, but much searching the interweb and looking at the electrical drawings, i note everything goes through the fuse box on drivers side (uk) it seems this may cause issues.
Also sometimes, when driving have the dashboard chime at me, but no warning lights - after which, when you turn the engine off, dead. Then again wait a while all ok again and you can start, drive use everything electrical.

Am I in the right area, and just take the fuse box out and replace with a new (or secondhand one) one. Are the fuse boxes the same throughout the models / years? Anything else worth checking or doing?

Many thanks
Dan

Hi, first of all check if the battery clamps are tight and main earth lead is well connected to body... if these are OK it's a bad contact somewhere, can be at the engine bay fusebox too, for the interior fusebox you need one removed from facelift D2, disconnect the battery negative lead before the swap then after reconnection turn ignition on 2(dont try to crank) and leave it so 5 minutes before doing anything else

sierrafery said:

Hi, first of all check if the battery clamps are tight and main earth lead is well connected to body... if these are OK it's a bad contact somewhere, can be at the engine bay fusebox too, for the interior fusebox you need one removed from facelift D2, disconnect the battery negative lead before the swap then after reconnection turn ignition on 2(dont try to crank) and leave it so 5 minutes before doing anything else

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Hi
Thanks for the info. I will make sure earths are all good. It is strange as it is really is like a computer reboot, totally dead, then few mins later all comes back on.
Does the passenger fuse box have an mcu in it out of interest?

Thanks for confirming I'm in the right area.

Many thanks
Dan

sonicm1etn said:

It is strange as it is really is like a computer reboot, totally dead, then few mins later all comes back on.
Does the passenger fuse box have an mcu in it out of interest?

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Next time when it happens turn on the headlights and push the horns and if those are dead as well it's a main power supply issue not the interior fusebox cos the horns are not conncted to that

i dont know what you mean by mcu , the interior fusebox is called IDM(inteligent driver module), a very complex unit

sierrafery said:

Next time when it happens turn on the headlights and push the horns and if those are dead as well it's a main power supply issue not the interior fusebox cos the horns are not conncted to that

i dont know what you mean by mcu , the interior fusebox is called IDM(inteligent driver module), a very complex unit

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Hi
I will do that when it does it again to check, but in the mean time will look at the earth drawings and go hunt them to make sure they are clean, starting in the engine bay.
mcu short for micro controller
Out of interest is there any documentation about the idm in the fuse box

Cheers

sierrafery said:

Next time when it happens turn on the headlights and push the horns and if those are dead as well it's a main power supply issue not the interior fusebox cos the horns are not conncted to that

i dont know what you mean by mcu , the interior fusebox is called IDM(inteligent driver module), a very complex unit

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Hi
As it done it a few times today, I have checked what you suggest, the horn does not work when the car is 'dead' so will look at the earths and engine fuse box.
However when I turn the head lights on (horn still not working), everything else restarts, and everything works, horn etc ok. so it seems the head light load is just enough to make a suspect connection / earth. Any suggestions to the best place to look, obviously going to start at battery and main chassis engine earth there.

ta

sonicm1etn said:

Any suggestions to the best place to look, obviously going to start at battery and main chassis engine earth there.

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Yes, that's a good place to start, next is the engine bay fusebox power connections or it can be a bad contact within it

sonicm1etn said:

Out of interest is there any documentation about the idm in the fuse box

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i dont know much about the cip, unfortunately i dont have a clear enough picture, i'll take a better one when i get in there again, looks like this

As above but also check for water/damp around modules in passenger footwell.