C4 Picasso (B78) Economy Mode

[ChrisW]

Hi,
I am really not sure if I am doing this right but here goes.
Recently when my c4gp MK2 has been left for more than about 30 minutes it goes into economy mode and shuts everything but the lock system down. After repeated pushes of the start button it starts and runs perfectly. A local specialist did a diagnostic but only charged me half as they weren't sure of the result. They suggest changing the voltage sensor which is built in to the negative battery cable at a cost of £450 as a starting place. Could you give me the part number I think I will get one from a breakers and try it myself. My vin is VF7**************[VIN obfuscated, can be read by forum staff]
Many thanks in anticipation.
Chris

[RichardW]

We had a similar thread recently on a DS5, but I don't think a solution was ever posted. Really you would need to catch it in the act on the diagnostics to see if the computer is seeing the button being pressed. Eco mode is normal, and shouldn't affect re-starting. In the absence of any other data, I'd be thinking about replacing the part that appears faulty, i.e the start switch!

[GiveMeABreak]

Your vehicle has one of the more complex energy managements systems on as it has an energy accumulator system for the Stop Start.

This can make troubleshooting more complex as there are additional factors to consider.

I'll suggest one immediate thing you can do, which has been responsible for a lot of these issues.

Check your passenger compartment fusebox (you'll need a torch). You are looking for the SHUNT fuse. If you can see one, ensure it is in the 'Client' or 'Customer' position. Garages / owners who check fuses can often pull them out an put them back in the wrong place. In this specific case, the shunt fuse may be in the 'Park' position in which case it shuts down most energy consuming equipment as soon as the ignition is switched off.

This sounds on the face of it exactly what is happening. So a quick check of this will confirm the fuse setting. Let us know the outcome.

[ChrisW]

Thanks for your quick responses. I will check the fuse and button but don't think it will be that as this problem seems to come and go . Everything works perfect for weeks then it starts happening. It does seem to happen more when the temperature rises a bit. Its been doing it for 3 days , now today perfect so far. When I come to the car and unlock nothing but the locking works. The mirrors stay folded and the boot wont open for instance. Sometimes it will start on a press. Others I will be pressing 10 or 15 times, then it runs perfectly with stop/start working only 100 yards away at the end of the street. When it starts it briefly flashes a red warning about the charging system and sometimes tells me to check front fogs. I turn them on and that goes away. Ready to pull my hair out , whats left of it lol.

[RichardW]

https://www.frenchcarforum.co.uk/forum/ ... hp?t=73480

Almost identical; even down to the charge system fault and front fogs failure warning! Unfortunately OP didn't come back to tell if resolved, but the charge management unit was changed without resolution....

That it seems 'dead' to start with, suggests that something is pulling the network down, as to what.....????

[GiveMeABreak]

Bear in mind that this system has the Ultra Capacitor ECU with all the other gubbins behind the front left wheel arch. If the capacitor has gone then it will affect the Stop Start operation and of course may be related to the cause of the drain. I don't have enough technical info on this specific system being the later version employed, so given the complexity and of course the link that Richard referred to regarding the BCSU making no difference, it may be more cost effective in the long term to let Citroen have a look rather than replacing parts and paying third party garages more diagnostic fees.

[RichardW]

Seems to be not unknown, and maybe a fault with connections to the battery fusebox...http://c4owners.org/plugins/forum/forum ... php?240142

[ChrisW]

Looks like a typical Citroen can of worms . I think you may be right Marc. I will carry on with it for now as it always starts even though it may take 5 minutes. If / when it gets worse go to Citroen. So annoying as I love the comfort and relaxed drive.
Thanks again both.
Chris

[GiveMeABreak]

Seems to be not unknown, and maybe a fault with connections to the battery fusebox...http://c4owners.org/plugins/forum/forum ... php?240142

Well spotted Richard and this would indeed seem indicate a fusebox issue. Annoyingly his video link is no longer valid, so I can't identify which one he is referring to.

[ChrisW]

I thought I had looked everywhere, this link is my problem exactly. Great work Richard. Hmm. I suppose I should clean all the connections on the battery fusebox as others seem to have done to start with. Could you give me the part number for that box Marc, I can keep my eyes open for a used item perhaps.

[GiveMeABreak]

Ok, so here is the issue Chris. As I don't know which component was actually replaced, I can't tell help with the correct one, but here are the possibilities:

(1) The Engine Fusebox itself, part: 9810296380, £402.26
(10) The Switching and Protection Unit, part: 9801916680, £54.30
(30) The Protection and Management Unit, part: 9675349880, £348.16

If it was my money it would be either (1) or (30)

All prices VAT inclusive direct from Citroen. It may be worth trying to contact that member on C4 Owners and seeing if he can advise - or get advice from Citroen.

[ChrisW]

Thanks Marc, you have gone above and beyond, I agree with your assessment. It seems there is no easy or cheap option. I will do as you suggest and meanwhile live with it. If the fault was on all the time it would be Citroen. I simply can't afford to spend in excess of £400 on the wrong part. Rest assured I will report back. It is a shame when people don't do so. Too many happy to take help and not provide it.

[ChrisW]

A search of the link brings up the you tube video. It's number 30. There are a few about for £75 or so used. I will get one and, once the weather improves, it looks a simple enough job. I will let you know how it goes.

[GiveMeABreak]

Ok, let us know how you get on.

[ChrisW]

I have a used battery fuse box ready but it hasnt come up with the fault since. I will wait , it will be back its a Citroen lol. I want to change it and see a result or not