Citroen C4 my key will unlock doors but car won't recognise it to start unless i take + off main battery then put it back on i've since put a new battery on and still same

Have you replaced the car battery or was it key fob battery ?

I've replaced the key batteries 1st and then the car battery..it worked fine for 2 days after putting new battery on but now back to not working

Try resynchronisation procedure


- Switch off the ignition and take out the key
- Wait 1 minute without pressing the buttons of any remote control
- Place the key of the high frequency remote control to be synchronised in position "ignition+"
- Within 10 seconds, press the locking button for 5 seconds
- Switch off the ignition and take out the key
- Repeat the procedure with the other keys from point N°3, otherwise move on to point N°7
- Wait 30 seconds, the remote controls are synchronised

Sorry forgot to say its a stop start as well

There are a few stop / start related fuses you may want to check

Citroen C4 Picasso mk2 (from 2013) – fuse box diagram
Year of production: 2013, 2014, 2015, 2016

Fuse box under dashboard
The type of electrical of the vehicle depends on its level of equipment. To identify the type of electrical system on your vehicle, open the bonnet.

TYPE 1: electrical system does not have any fuses in front of the battery

TYPE 2: presence of an additional fuse box in front of the battery

Type 1 fuse box
Fuse box number 1
Fuse Ampere rating [A] Function
F8 5 Steering mounted controls
F18 20 Touch screen tablet, audio and navigation system, CD player, USB ports and auxiliary sockets (AUX)
F16 15 Front 12V socket
F15 15 Boot 12V socket
F28 5 START/STOP button
F30 15 Rear wiper
F27 15 Front screen wash pump, rear screen wash pump
F26 15 Horn
F20 5 Airbags
F21 5 Instrument panel
F19 5 Rain and shunshine sensor
F12 5 Keyless starting unit
F2 5 Manual headlamp adjustment control
Fuse box number 2
Fuse Ampere rating [A] Function
F9 15 Rear 12V socket


Type 2 fuse box
Fuse Ampere rating [A] Function
F3 3 START/STOP button
F6A 15 Touch screen tablet, audio and navigation system, CD player, USB ports and auxiliary sockets (AUX)
F8 5 Alarm
F9 3 Steering mounted controls
F19 5 Instrument panel
F24 3 Rain and sunshine sensor
F25 5 Airbags
F33 3 Memorisation of diving position
F34 5 Electric power steering
F13 10 Front 12V socket
F14 10 Boot 12V socket
F16 3 Map reading lamps in row 1 courtesy lamps
F27 5 Electronic gearbox gear selector
F30 20 Rear wiper
F38 3 Manual headlamp adjustment control
Fuse box in engine compartment
Type 1 fuse box
Fuse Ampere rating [A] Function
F18 10 Right hand main beam
F19 10 Left hand main beam
Type 2 fuse box
Fusebox 1
The fuse box is place in the engine compartment near the battery (left-hand side).

Fuse Ampere rating [A] Function
F9 30 Motorised tailgate
F19 25 HIFI amplifier
F21 3 Hands-free starting reading unit
Fusebox 2
An additional fuse box is fitted in front of the battery (fob type 2).

Fuse Ampere rating [A] Function
F19 30 Front wiper slow/fast speed
F20 15 Front and rear screen wash pump
F21 20 Headlamp wash pump
WARNING: Terminal and harness assignments for individual connectors will vary depending on vehicle equipment level, model, and market..