C5 WONT SRART AFTER HITTING POTHOLE

[cowmechanic]

Hi, I hit a pothole about 3wks ago with front nearside wheel , car kept driving but hazard lights came on , wipers operated, lights remained on but wouldn't dip . I then stopped and the car at a garage about a mile later and it wouldn't restart ,it will crank but none of the electrics work apart from drivers window, the hazards remain on all the time . only fault I can find is that it immediately blows f8 in the glove compartment which is particulate additive pump additive and tyre inflation sensor. I have had two local techs plug in their laptops but none the wiser. have disconnected Eolys sensor at tank . My mechanic friend thinks there is a short in the loom. car is a 2006 face lift c5 2.0 hdi 138 vtr, any help appreciated with 160k thanks

[lexi]

I take it you have redone all earth connections at battery /gearbox etc.
Check and break all fuses. Do BSI reset. Follow procedure for battery disconnection and reconnect. Make sure battery is top condition. Then it will be Lexia and a multimeter to check component and loom sections.

[dnsey]

It wouldn't explain the other odd behaviours, but is there an impact sensor which cuts off the fuel pump? If so, resetting it might get the car running again.

[Stickyfinger]

Dislodged fuse/control box ?

[wurlycorner]

I would start with checking all the battery connections, earths, fuse box and relays etc. are still tight, as others have suggested.

[cowmechanic]

I have so far removed ecu and fuse box and examined loom in engine compartment , I have tried to reset bsi but when I reconnect battery there is a large current draw and as soon as the ignition is turned to the first notch the hazards come on , the wipers complete one cycle , the electronic display is blank . This car is too good to scrap but I don't want to throw to much money at it I have now put my old mk1 c5 back on the rd incidently which is a far better performing car ! I remember when my wife had a minor ding in a saab in which the air bag went off and hazards came on and it wouldn't start

[Stickyfinger]

Have you taken out and reseated the lower fuse box....it is part of the "system"

Either that of use one of the "Home Call" auto electricians......normally they are very good at this type of work and garages often use them.

[wizaird]

Did this get sorted.... Mine is a similar affair... Same model same year... Went over a little bump and it died...... Turns over but won't start..... High pressure pump isn't pumping... Nothing at the injectors.... Completely dry.?

how did you get on?

Thanks Dave

[GiveMeABreak]

Heard this happening a lot with pot holes and in many cases it was the impact sensors that were triggered. Causing amongst other things the fuel cut off to the engine, which could be why you aren't getting any through. On the early Picassos there was a red switch you could pull to temporarily start the engine. You could bridge the circuit with a piece of wire to test whether it was this preventing the car starting. However on newer cars the reset is managed by the ECU and will need the Lexia/Diagbox to do this. Must of been quite a wallop!

[Stickyfinger]

How does a ECU detect a "shock" ?

[wheeler]

There is no inertia switch on a C5, the fuel cut off in an impact is managed by the airbag ECU. It normally resets simply by switching the ignition off then back on.
Does the airbag ECU show any fault codes ? might be worth trying to disconnect the airbag ECU & see if the fuse still blows.
We really need to know everything that's on the F8 circuit, the handbook doesent always list everything.

[GiveMeABreak]

How does a ECU detect a "shock" ?

Via the impact sensors usually found in or near the front bumpers on some earlier Picassos.
http://ebay.co.uk/itm/CITROEN-C5-IMPACT ... 0928889892
I'm in town, but will check when I get back to see where they are on this car

[GiveMeABreak]

How does a ECU detect a "shock" ?

It seems the Airbag ECU sends impact information to the BSI - and this in turn uses the information to determine what needs to be done -
Cutting off Cruise Control
Emergency Door and Boot unlocking
Fuel pump cut-off function
Automatic switching on of Hazard lamps
Emergency Call request (according to equip and country of course)

The BSI will communicate with the Engine ECU and can send the command to cut off the 'Boiler' relay.
At least 2 of the items above seem to fit with the issue.

Airbag ECU
The airbag ECU is fitted with internal and external acceleration sensors(lateral sensors).
The airbag ECU analyses the signals that it receives.
The air bag ECU carries out the processing operations to determine the accelerations and the direction of the impact.
The air bag ECU decides whether or not to fire the pyrotechnic components to which it is connected.
The main functions of the airbag ECU for direct protection of the occupants are :
The detection of front, side and rear impacts
Selective triggering of the pretensioners, front airbags and side airbags

I wouldn't go fiddling about with any of the airbag circuits or putting an ohmmeter as this can trigger the system. As suggested by others, the cheapest and most sensible option is to get it hooked up to the lexia and see what comes off. It maybe that the system can be reset if it is indeed one of the above components that has been triggered. If not, it will help point you to other possibilities.

[cowmechanic]

I never got car started again, it has various types of pennicillen growing out of the interior trim at this stage. Car is undercover and I would still like to get it going as the back axle in my 2004 c5 is knackered and I managed to burn off two back tyres in 7000 miles! . Where is the airbag ecu and what would happen if I disconnected it

[GiveMeABreak]

If I were you, get the car battery charged up, then follow the BSI reset procedure on the Forum, then try and get somebody with a Lexia to run a test, clear the faults, re-run it and start from there. The system should be able to be reset with the Lexia assuming it is this at fault. Better to try this first before tampering with the airbag ECU until you know it that for sure.