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C4 - DS4 Owners :: Forums :: Citroen C4 Picasso and Grand C4 Picasso (B78) 2013 onward :: C4 Picasso and Grand C4 Picasso (B78) Problems and Issues

Eco won't stay on

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Fri May 31 2019, 02:14pm
Member No: #574
Joined: Jul 08 2007
Location: Dorset
iscom wrote ...

I think if you keep the aircon on the eco won't work

Sorry, it doesn't (well, climate anyway). It is certainly one of the factors the system takes into account, and it may prevent the engine stopping if the aircon is under heavy load, but it certainly will stop with the climate on.
Fri Sep 27 2019, 10:44am
Member No: #33760
Joined: Jan 07 2014
Location: podgorica
Battery is not fully charged or test the battery!
Sun Aug 14 2022, 01:00pm
Member No: #59996
Joined: Aug 13 2022
Location: South Africa
HI all,

I have had issues with the start stop (SS) system and thought I would share the faults and how finally it will be repaired.

The SS has a Ultracapacitor and SS ECU module under the fender next to the battery. You can only get to this system by removing the wheel and wheel arch black trim.

The system consists of a 5V Ultracapacitor (2x 2.5V Ultracaps in series) and the SS ECU that switches in the Ultracapacitor booster to restart the car in 400ms via the reverse motor alternator. Yes, the restart is via the alternator with 4KW of kick from this Ultracapacitor.

Current faults:
P1AA2 - Voltage Retaining Device: Internal Electronics Fault
P1A9C - Energy Accumulator: Accumulator State of Health Fault

I will upload pictures once a member of the Ultracapacitor and SS ECU. I have purchased these second hand and going to replace both units.
2 User said Thank You to EdMonty for this Post :
 iscom (14 Aug 2022 : 13:29) , Mel4 (09 Nov 2022 : 05:35)
Mon Oct 31 2022, 07:44am
Member No: #60176
Joined: Oct 14 2022
Location: Finland
@EdMonty did you fix the issue? I'm having the same problem with my C4 2012 1.6hdi

Fault codes P1AA2 and P1A9C came after alternator belt snapped. I have checked the wirings for any damage but everything looks okay apart from the connector plug to the crankshaft position sensor which was shattered but it was repaired by a mechanic.
Wed Nov 09 2022, 05:39am
Member No: #60243
Joined: Nov 08 2022
Location: Brisbane
Hi did you get this error problem fixed I have the same error P1A9C after replacing the battery and accumulator capacitor for the stop and start system.
Thu Dec 29 2022, 11:15am
Member No: #51643
Joined: Jul 15 2018
Location: Wakefield
What finally fixed mine after the Citroen dealer wanted to charge me £500 as they said it wasnt my battery and needed to investigate was a new battery. Followed a youtube video on how to remove it. Was a bit of a hassle due to its positioning but after watching the video carefully took me about an hour. Eco now working.
Sat Jan 14 2023, 05:14am
Member No: #60176
Joined: Oct 14 2022
Location: Finland
Do you mean you changed the ultracapacitor?
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