citroen xsara picasso ecu faults

A forum for new members to introduce themselves to the rabble already onboard. Not compulsory!
Tell us a little about yourself, lie if you have to but keep it to just an introduction, not a car discussion.

Moderator: RichardW

New User
Posts: 0
Joined: 13 Oct 2021, 08:25

citroen xsara picasso ecu faults

Post by sumo »

hi to all you citroen sufferers/ owners

ecu faults petrol guage/radiator fans

i bought a xsarpic 07 plate that was in reasonably good body and enginewise but had a few of the usual faults...

the lad who i baught the car from said since the mot in october 20 (i got car feb21) it stalled alot run eratic and when left ticking over it would die....

turns out that after alot of trial and error the ecu in the right wing under bonnet area isnt funtioning properly

the first problem is/was the af sensor it was gunged up and a new part from gsf sorted the choppy running.
second problem was simple the car was running on fumes most of the time i filled it up and drove the pic for a couple of hours without any faults . noted fuel guage readings where out . pre fill guage at 3 bars i put in 40 ltrs and it went to full but dropped a bar to 7 bars in ten mins.
also noted that sitting in traffic the temp guage went to three bars then stalled once. restarted after a few turns of the key then was ok
no faults logged on ecu reader.
now heres the interesting bit
i changed the temp switch/sensor on the thermostat housing still no fans
ac no gas so preasure switch on ac not switching on operation for fan full speed operation bridged the switch still no fan operation
turns out that psa fitted a overhead failsafe so the engine stalls at over max operational temp . i think the fuel pump stops as one time this happened i pressed the fuel rail bleeder valve and it took some time to purge.
the relays wont switch on the front panel no matter what si i removed cleaned and replaced both and them both and the slow speed resistor pack and still no operation . at this point i checked the voltages at every point from the ecu 12 v and then bridged the connections on both of the relay points and hey presto fan runs at high speed and low speed .

now to cut out the radiator problem

ive fitted an after market temp switch on the high speed circuit and a bridging switch into the cab on the low voltage side

temp guage ok fuel guage eratic rad fan works on at 95° off at 85° plus the switch for hot days and traffic.......

fixed for £50
User avatar
white exec
Moderating Team
Posts: 7489
Joined: 21 Dec 2015, 13:46
x 1467

Re: citroen xsara picasso ecu faults

Post by white exec »

On some of our vehicles (from mid-90s onwards) the engine (fuelling) ECU - which also controls cooling fan and AC operation - is programmed to progressively reduce fuel injection as the sensed coolant temperature goes very high. This is a safety feature, to prevent engine destruction by overheating.