2007 xsara picasso 1.6 petrol with throttle pedal incorrect value!

[Darren mills]

Hi all, new here but in need of help!
I have a 2007 citroen xsara picasso 1.6 petrol
That sometimes starts, sometimes doesn't! Doesn't always idle and when it does it doesn't rev correctly,
Have had it plugged in to lexia and got the codes p1158, p0121 and p0122, i have checked all wiring, connections, replaced throttle pedal and throttle body but still lexia is telling me that the throttle value is incorrect and doesn't change pushing the pedal! Lost with this one so any help would be greatly appreciated,

[wheeler]

Disconnect the 3 ECU plugs & check for any signs of water or corrosion on the pins.

[Darren mills]

No signs of any water damage! Have managed to get it running now with no fault codes appearing, but still saying incorrect value for throttle pedal position?? It does occasionally flick to idle, mid throttle, full throttle but doesn't stay there!