power steering gave no warning then stopped giving power

Ozvtr wrote: ↑Mon Jan 06, 2020 11:05 pm My assumption would be that there was a bad connection between the steering ECU and the wiring connectors or between the BSM and the wiring connectors and you have fixed the connection by disturbing it. My guess is at the BSM. My recommendation would be a liberal squirt of "moisture displacement spray" on those connections. I would also look very carefully at the associated pins in the BSM and steering ECU for corrosion or damage.
At least you know it's NOT the ECU, it is unlikely that has gone intermittent.

So it looks as if we have discovered it isn't either the rack or the motor, which is great, nor the ECU which is also great.

I note that you have not said that the "reset" might have cured it, which I find interesting, as that is the conclusion I leapt to, and was not happy about.
I have to say that the underbonnet area is very clean and dry, plus the vehicle has only done about 60k miles but I am aware that a loose or dirty connection can come about in a variety of ways. I have yet to check the connections to the rack/motor, which as you now know gave a very low resistance reading, thinking that the recent work to the ARB may have disturbed them. And also, although the battery is in fine fettle, I have yet to test the alternator which really is an easy job and I will do very soon.

What also concerns me is that I have yet to discover where the sensors are that trigger the action of the rack motor via the ECU. I am concerned that one or more have these may have been damaged slightly when the car left the road. The front wheel hit the earth in the field hard enough to kick back and tear a ligament in my wife's thumb, so I worry that this shock may have caused further damage.
The vehicle is a 54 plate Pluriel with the 1600 petrol engine and sensodrive. Can you or anyone tell me where the steering ECU gets its signals from?
If it is to do with the ABS I have some experience of this (Land Rover Discovery 2) and am aware that reluctor rings and sensors do not tolerate too big a gap. Also, if it is the drive sensor, near the right-hand drive shaft, it was the right-hand wheel that hit the ploughed field, so that would make sense also if the drive shaft transmitted a shock to the drive sensor. But this was two summers ago.
The third thing is the slight squeak that we can hear when manoeuvering at low speeds, i.e. turning the wheel when parking. It isn't always there and it is not there now. It could still be not very much, but it could also be something. Wish I knew more about electric power steering!

Anyway, one thing I am thinking of doing first is to download, and pay for the Citroen diagnostic to go in my Foxwell scanner that I use with the Discovery.
If there is anything to report I will do so.
In any case, I am still very grateful for all help.
Cheers
Stan

Hmm where to start with this one?

Up to 2005 the C3’s ran CAN (controller area network) and VAN (vehicle area network) communication networks between the various ECU’s . The BSI acts as a “go between” for the two networks.

In late 2005 the VAN bus was changed to CAN bus. So they are all CAN bus.

The engine, ABS and steering ECU’s are on the (first) CAN network. The ABS ECU sends speed information to the engine and steering ECU’s (and other places that are not relevant). As far as the steering ECU is concerned this speed information tells the steering ECU when to, or not to, add assistance to the steering. So, low speeds - lots of assistance, high speed - not so much. A failure of the ABS system will “turn off” the steering ECU but you will get an ABS light and you will not get a reading for speed on the dash. This does not seem to be your case.

A torque sensor is used by the steering ECU to quantify how much torque (effort) is being applied to the steering wheel by the driver. The torque sensor sits on the top of the steering box and is physically connected to the steering shaft and consequently the steering wheel. There are 2 big wires going to the steering rack motor and 5 small wires going to the torque sensor on the steering rack. The torque (driver effort) and speed information are compared inside the steering ECU. The steering ECU then drives the steering assist motor until the predetermined desired torque (driver assistance) for that speed, is reached. Of course this happens very quickly and all you feel is the steering feeling lighter.

The assisted steering system seems to be very reliable (because its Japanese?) but the waters are muddied by people who post faults and do not follow them up. So it's hard to build up some sort of picture. A lot of "under bonnet" faults seem to come from salty water getting into the connectors and corroding the pins. The only thing I can tell you that's common with the failure of the steering system is that a battery in poor condition causes failures. We know in this case it's not that, so apart from bad connectors there are no other "known" faults and you'll have to do some digging because, well, you are in uncharted territory. Perhaps there is a failure in the ECU but until you (or someone in a similar situation) comes back and tells us what the failure was, we will have learned nothing.

I am a technician by trade and I can tell you ANYTHING CAN FAIL AT ANY TIME! Unfortunately that is no help. If you have test equipment, circuit diagrams and an understanding of the principals involved in the operation, you have a good chance of tracking down the fault very quickly. But you have none of those, so you play the odds game. What are the likely suspects and what are the odds? What are the odds it's a software bug or corroded pins? Which is the easiest to try first? Replacing the ECU or checking the battery? Do you see what I mean? You have to start with the easiest and finish with the hardest. It might seem like a waste of time but some faults give you NO CLUES. You are going to feel pretty stupid if you replaced the ECU and its just a popped connector. But then again it can be a blown ECU. Being a technician I will (if practical) autopsy ECUs (or what ever) to find out what went wrong. To be honest most of the things that have gone wrong with my C3 have been mechanical. No recirculated air from the air conditioning-stripped gears in the servo motor. Engine runs like sh!t-stuck purge valve. Auto box clunks bangs and beeps-sticking modulator valves. And so on.

Phew, sorry for the long post.

I read this post right through as my own 2007 1.4 HDI has done the no assisted steering thing several times.
It just stops working and I fairly sure that the battery voltage or condition is not the cause.
The first time this happened I drove the car for over a week, daily to work and back, then suddenly one morning it started and had assisted steering again.

It has done the same thing twice since then, each time before I got it to the garage it has fixed itself.
It is of course extremely hard to find a fault that is not there anymore.
I have also had the car on test equipment and never found any codes stored for steering faults.

Over the seven years I've owned my C3 I have had several electrical issues, like a rear wiper that suddenly decides to wash and wipe the rear screen, without me doing anything.
The lights staying on when you rotate the switch to the off position is another regular fault, strangely switch the headlight on and immediately off again cures this.

Another oddity is the dashboard charge light, it goes out when the engine starts, even with the alternator belt removed.
That means if the belt snaps you will get no warning that it has happened.

Citroen C3 electronic Power Steering common faults fixes here C1400 or C1413

and the same solution but without the codes and the C3 power steering being intermittent (FIX)