[garysmith21]

Hi - hope someone can help.

My wife bought a 2008 E91 320D just a month ago and a few days ago it wouldn't start - it was cranking fine but not starting.

Using ISTA/D I read the fault codes and there were about 17 of them! Following the calculated test plan meant a check of the wires/fuses first and sure enough, the 30A fuse in the ECU compartment was blown. Replaced it and almost all the codes disappeared except one: dde 4954 control unit internal.

Car still cranks but doesn't start. The fuse hasn't blown again and still just the one code when reading the errors.

Using INPA, I got some more information from the error memory:

DC / DC converter defective, buffer capacitor 1 can not be charged
Test conditions met
Error currently available and already saved
Error would not cause a warning lamp to light up
Error is not registered in the shadow memory
Error is not entered in the history buffer

Anyone seen this before? I can't find much when searching.

Is this code also causing the non-start issue or is there something that isn't recording a code at fault?

Thanks for any assistance.

[Sensible_]

Originally Posted by garysmith21

Hi - hope someone can help.

My wife bought a 2008 E91 320D just a month ago and a few days ago it wouldn't start - it was cranking fine but not starting.

Using ISTA/D I read the fault codes and there were about 17 of them! Following the calculated test plan meant a check of the wires/fuses first and sure enough, the 30A fuse in the ECU compartment was blown. Replaced it and almost all the codes disappeared except one: dde 4954 control unit internal.

Car still cranks but doesn't start. The fuse hasn't blown again and still just the one code when reading the errors.

Using INPA, I got some more information from the error memory:

DC / DC converter defective, buffer capacitor 1 can not be charged
Test conditions met
Error currently available and already saved
Error would not cause a warning lamp to light up
Error is not registered in the shadow memory
Error is not entered in the history buffer

Anyone seen this before? I can't find much when searching.

Is this code also causing the non-start issue or is there something that isn't recording a code at fault?

Thanks for any assistance.

I would imagine the DDE is damaged. Is there any water ingress around the DDE ECU? Have you run the test plan in ISTA D to see what it suggests?

[garysmith21]

There is no water currently in the compartment - I checked when changing the first fuse. Haven’t checked to see if there had been water previously though so will go back to that.

The rest plan in ISTA D does say to replace the control unit and re-calibrate the injectors (or something like that - trying to remember from yesterday).

That does suggest ISTA thinks the DDE is dead doesn’t it? Although it is only showing as yellow in the tree and not red so it can’t be totally dead can it?

[garysmith21]

So took the DDE apart and one of the chips has burnt out - that'll be the issue...

[Sensible_]

Originally Posted by garysmith21

So took the DDE apart and one of the chips has burnt out - that'll be the issue...

Yep. Any photos out of interest? Perhaps it can be repaired.

[garysmith21]

Have contacted BW Chiptune but waiting for a response to see what they can do.

[garysmith21]

Pics added. Not sure how repairable it is!

[Sensible_]

Originally Posted by garysmith21

Pics added. Not sure how repairable it is!

Wow. Never seen that before.

There seems to still be communication with the DDE so you may be able to buy a used one and then clone your faulty DDE. This would be the cheapest option.

[garysmith21]

Interesting - how does that work? Do I get a second hand DDE, wipe it and then literally copy old DDE info to new one?

I imagine there’s special (expensive?!) software for that?