I have a 2006 Xsara Picasso SX HDi. Last summer it started having issues with the orange engine management light coming on every say 5 miles, for a while. During this period the car would go into 'safe mode' and slow down which was to annoying/dangerous if overtaking. Just once the problem cleared by itself on a long journey. I have an OBD2 computer checker with software and was able to find the fault myself and reset it. However the problem soon re-occurred. OBD2 checks said there was a problem with a fuel solenoid and another, I can't remember what as I gave up trying to solve the riddle months ago and just lived with the problem.
Anyway a week ago I found the solution quite by accident:
I removed the old (not working, as i didn't have the code) Citroen stereo and installed a new one. As I was outside I ran the battery down to absolute zero by listening to music and didn't start to recharge it for at least 2 hours. When I did charge it I used a reliable but cheap auto-charger which I left charging the car battery for some 24 hours.
Since then, when I started the car (no computer reset or anything done - it just sorted itself out) there has been no warning light whatsoever and all is running fine. This leads me to one of three conclusions:
1. The Citroen stereo is feeding back a signal into the car confusing the electronics.
2. The battery being totally flat for some hours has done a serious system reset.
3. The long charging period has given a slightly higher voltage than normal and caused some issue to clear itself.
Take your pick, I'm confused but happy. I waited a week before posting this to be sure the problem has gone - it has and the car is PERFECT now :)
Jules
March 2015