Citroen C8 2005 2.0 HDI sudden ECU power loss

[David_M]

Hi all, I have a C8 2005 2.0HDI and I have a sudden issue in that the ECU has no power.
Got out of it 8PM last Sunday no issues, went to start Monday lunchtime, as i turned key to start, central locking 'clunked' and elec fold mirrors whirred briefly but didn't fold (?!) Followed by Immediate "beep" with "immobiliser fault"message on LCD display. Cranks over but no start. Tried spare key. Same issue. After numerous cranking attempts It's now in economy mode, good new battery, I charged it for 18 hours, still in economy despite fully charged new exide battery about 4 months ago.
On the day it happened, before I did anything, and before it went into economy mode, i called out a professional mobile key coder and his scanner said "bsi pass/no fault" & "2 keys recognised" so not keys and not BSI ? however, he couldnt read ECU, was just a weird orange icon on his screen next to where it said ecu, he said ECU was dead, also, no EML at all on cycling ignition (when it worked before), so after research,online, i replaced BSM for used of same part number, checked every single fuse in the car (BSI, BSM, Battery compartment) including all Maxi's, unplugged ecu and ABS ecu to check pin corrosion and anything obvious, same for all BSI plugs, and same for BSM plugs, even removed BSI, opened that up just to have a look for anything obvious on PCB, BSM / BSI / ECU Multiplugs all very clean and dry. Everything works on the car, electrical rear doors, elec windows, interior lights, exterior lights, horn wipers central locking (windows radio and LCD info screen now dead cos in economy mode) Even have the key reminder when I leave key in ignition barrel and open the door.
So that's what I've tried so far. I desperately need my car, Please help! Thanks. .

[mickthemaverick]

You say it is a new battery, did you carry out the correct BSI reset procedure when changing the battery? If not try that now. The procedure is in the link below:

viewtopic.php?p=601679#p601679

[David_M]

Hi Mick, thanks for reply, It's in economy mode tho, so can't roll window down. Before it did, I tried bsi reset, no "bong" when turned sidelights on, so, dont know if it worked? New battery was put in about November without any bsi reset, just banged it in and it's been fine since.

[David_M]

I wonder can i do something to the door switch so that it thinks it is closed, to open the door instead? I read that a screwdriver to engage door lock mimicking the striker plate can make it think the door is fully closed.

[mickthemaverick]

If you connect another fully charged battery across the existing one it should come out of economy mode and allow you to open the window I believe

[David_M]

Right, I've just followed those instructions carefully about the BSI rest, I locked car door by moving the latch down manually while it was open and central locking worked to lock and unlock the car so it did think the door was shut when it wasnt. So that's just the same as having window down I'd think.
Anyway, no bsi reset worked in getting the EML to illuminate and the car just cranks over but will not start. Any other things to try next? I have a little autel scanner (basic) and a multimeter.