C4 MK2 P1A9C

[gango67]

Hi All
Have a C4 where start / stop won't work used diagabox comes up with fault code P1A9C ( Engine Accumulator state of health ) tried to remove start stop function in BSI config but still get the service light on and engine Fault beep message is there a way to check the accumulator health within diagabox attached is a photo which may assist in helping

[GiveMeABreak]

See my posts here: viewtopic.php?p=795931#p795931

[gango67]

Hi Marc
thanks for the reply yes i did read that post previously i just wandered if off the pictures anyone can tell if i need a new battery or to remove the inner wing shield and assume check all connections are good there ?
i was looking at diagbox but couldnt see anything about re-initiallising capacitor
any help guidance appreciated
regards
Mark

[gango67]

According to 2nd pic says ancillaries battery at 61 % is that my main battery or reference to the ultra capacitor charge and also says battery charge estimation status Nominal and battery charge status level Bottom ? Not really sure what these references mean
So was wandering should I change AGM battery or Ultra capacitor or remove inner wing and wheel and check the connections if the pictures give an indication of direction to go

[GiveMeABreak]

Ancillary battery refers to the main 12V car battery.

Just be careful if you go digging about with the ultra-capacitor as these MUST be discharged before dismantling using appropriate tools - as they carry a powerful residual charge.

[gango67]

Ancillary battery refers to the main 12V car battery.

Just be careful if you go digging about with the ultra-capacitor as these MUST be discharged before dismantling using appropriate tools - as they carry a powerful residual charge.

Thanks again Marc for replying so at 61% that would indicate it may be low would you recommend driving around first to see if it improves charge status also as per your thread I get the message so need to check connections I assume that's on the ultra capacitor and ECU
Thanks
Mark

[gango67]

This is what I am referring to
"If you are getting a message "Engine Fault: Have the vehicle repaired" and a fault code of P1A9C, then the energy accumulator terminals need to be checked for tightness and if all are in order, the "Reinitialisation of the central voltage maintaining device" procedure needs to be undertaken using the guided procedure in Diagbox."

[GiveMeABreak]

Yes, - regarding the main 12V car battery, it it's 5 years old or over, time to replace its capacity to hold a full charge diminishes over time as the cells degrade.

As for the above quote - that's from Citroen's own technical bulletin concerning the conditions of this fault code appearing. There should be a guided procedure in Diagbox for this - but where it is I can't advise. You may need to do a global test first, then locate and select the relevant voltage maintaining device ECU, select that and it should provide further options. But I don't have this system, so can't be specific.

[gango67]

Yes, - regarding the main 12V car battery, it it's 5 years old or over, time to replace its capacity to hold a full charge diminishes over time as the cells degrade.

As for the above quote - that's from Citroen's own technical bulletin concerning the conditions of this fault code appearing. There should be a guided procedure in Diagbox for this - but where it is I can't advise. You may need to do a global test first, then locate and select the relevant voltage maintaining device ECU, select that and it should provide further options. But I don't have this system, so can't be specific.

Thanks again will have a delve into it more on the weekend and try and check the tightness of connections and wiring it's weird as when I do a global test I get the highlighted voltage ECU with description of ECU present but not configured absent and when I go into BSI I can't see an option to change it

[gango67]

As attached

[GiveMeABreak]

Hmmm.... I wonder if somebody has been there before....

[gango67]

Hmmm.... I wonder if somebody has been there before....

Maybe

[gango67]

That's the power unit config that shows it present

[GiveMeABreak]

That's just relating to the engine system, not the Stop Start System

Friendly Note: Just be very careful as you're in write mode - I wouldn't make any changes without knowing what you're doing as there's no undo option. Some things don't mean what you think they may and have to be left at certain values, or you'll end up with a non-functional car. I've seen a few cars looking like Christmas tree lights as a result - so track anything you do with existing values and the menus you are in so you don't forget later.

[gango67]

That's just relating to the engine system, not the Stop Start System

Friendly Note: Just be very careful as you're in write mode - I wouldn't make any changes without knowing what you're doing as there's no undo option. Some things don't mean what you think they may and have to be left at certain values, or you'll end up with a non-functional car. I've seen a few cars looking like Christmas tree lights as a result - so track anything you do with existing values and the menus you are in so you don't forget later.

Thanks Marc yes aware was in the write section always take pics of values before I even attempt to change anything I assumed the start stop and energy were showing that they are configured in that pic of the engine BSI I just need to dig around a bit further into engine ECU perhaps and see if I can find where the start stop ECU is not configured I found the reinstallation point for the start stop but battery charge has to be above 75% to proceed with it so left that for now would just love to get rid of the service light and beep with engine fault message not too worried about the system working or not thanks again for the advice greatly appreciated