320d not starting - dde relay?
Discussion
Non-functioning car this morning 
2007 320d N47/177bhp
Turns over but doesn't start.
Warning symbols come up to let me know that the tyre pressure/cruise control/stop start/etc are not working.
Diagnostic tool will not connect to the engine management, but will connect to other modules.
So it looks like an issue with the ECU - but if the ECU was dead, I wouldn't expect it to be turning over?
A bit of googling suggests that turning over but not starting is most likely down to a relay 'DDE relay'
Does this sound sensible? It would certainly be a lot easier than trying to trace a wiring fault.
What does this DDE relay do? when does it activate and what does it control? What I don't understand is why the car is turning over if the ECU is dead or not getting power.
2007 320d N47/177bhp
Turns over but doesn't start.
Warning symbols come up to let me know that the tyre pressure/cruise control/stop start/etc are not working.
Diagnostic tool will not connect to the engine management, but will connect to other modules.
So it looks like an issue with the ECU - but if the ECU was dead, I wouldn't expect it to be turning over?
A bit of googling suggests that turning over but not starting is most likely down to a relay 'DDE relay'
Does this sound sensible? It would certainly be a lot easier than trying to trace a wiring fault.
What does this DDE relay do? when does it activate and what does it control? What I don't understand is why the car is turning over if the ECU is dead or not getting power.
It was flooding.
Not the ECU though. The battery bay was full of water and the two cables that run out the bottom were corroded. One still intact but in poor condition and the other had broken.
It does seem stupid that BMW put the electrics in the lowest point of the car and then didn't put a drain hole in there.
I need to work out where the leak is, but for the moment replacement cables means the car runs again.
The internet says that this is a really common issue so I guess anyone with a 3/5 series at least should lift the battery and put a drain hole in.
In my case there are two plastic plugs but they might be glued because they only came out when I broke them.
Not the ECU though. The battery bay was full of water and the two cables that run out the bottom were corroded. One still intact but in poor condition and the other had broken.
It does seem stupid that BMW put the electrics in the lowest point of the car and then didn't put a drain hole in there.
I need to work out where the leak is, but for the moment replacement cables means the car runs again.
The internet says that this is a really common issue so I guess anyone with a 3/5 series at least should lift the battery and put a drain hole in.
In my case there are two plastic plugs but they might be glued because they only came out when I broke them.
The battery was underwater and one of the main power cables had corroded through.
It seems that there is a vent which allows water into the battery sump. You can see it if you strip out the trim in the boot.
I fixed by replacing the cable and drilling some drain holes in the battery sump.
Your problem could be the blue relay which is a common issue, but water getting into the battery sump is also very common.
It seems that there is a vent which allows water into the battery sump. You can see it if you strip out the trim in the boot.
I fixed by replacing the cable and drilling some drain holes in the battery sump.
Your problem could be the blue relay which is a common issue, but water getting into the battery sump is also very common.
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