Citroen C3 2007 loosing Power Steering

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terbo
TwoWaves
TwoWaves
Posts: 69
Joined: Sun Jul 06, 2014 2:40 pm

Citroen C3 2007 loosing Power Steering

Post by terbo »

Hi,
The Car of a friend looses its Power Steering from time to time.
Some times after Cold Start, some times after driving.
When you restart a few times or let it idle, it works again.

When the Power Steering does not work, you can not communicate
via Diagnostics with the EPS-ECU.

So he was told at the Dealer "EPS-ECU is bad" , so he got a used one,
put it in and drove , same Problem, got a second one, put it in,a few days
later - same Problem. Went back to the Dealer - "You need a NEW one".
OK, Steering is important - ordered new one , put in - fews days - you know it :)

Drove by after Work, just to take a quick look and took quick snapshots.
Only had small time window because was getting dark and Batterys of Flashlight going down.

One when no EPS was a no-comm, one when it was reachable,but both without Engine on.
I made a third one with Engine on and EPS Working, but somehow hit up the timeframe :(

Red+Blue = CAN ; Green = Output Positive from EPS-ECU to EPS-Motor.

When not reachable i can see the Baseline of both CAN-Lines is lower, and it
has this strange "Drift-Down" at the End. But what does this tell me ?
I am pretty sure, it is not going to be the EPS-ECU :)

All other ECUs are reachable , even when EPS is not working.

We checked the big Power going in - always normal Voltage - hooked up a
4 Amp Test-Light (only had this with me) and did not dime, even when EPS
was "Dead".

Greets Chris
Attachments
Car running with steering.psdata
Car run,EPS active, turning Steering
(3.54 MiB) Downloaded 536 times
CAN-nio.psdata
CAN not ok - EPS not working
(1.46 MiB) Downloaded 513 times
CAN-io.psdata
CAN-OK , EPS working
(1.42 MiB) Downloaded 520 times

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 1581
Joined: Sun Aug 25, 2013 7:22 am

Re: Citroen C3 2007 loosing Power Steering

Post by Steve Smith »

Hello Chris and thank you for the post, sorry for the late feedback.

I am not sure how far you are along with this one and no doubt my next reply will be late too.
With that said I have a few questions.

Before we dig too deep, do we know if this vehicle has any relevant bulletins regarding this issue?
I ask because you mentioned “Sometimes after cold start”.

It is at this point (Start-up) where CAN nodes will check who is online and announce their presence, whilst also ensuring their internal configuration is applicable for the vehicle in which it is fitted. (One ECU can fit multiple vehicles but configured accordingly)

In scenarios where the power up supply wire to the EPS ECU is different (originates from another source/connector) to other ECU’s we could have an event where momentarily, the EPS is offline due to delayed power up whilst the other ECU’s are present and “looking” to determine who is online.

Most certainly PCM, ABS and EPS will have high priority and if EPS is not online at Start up, the fail-safe will be EPS off and warning lights on

I think it would be worth checking the power up (supply) timing between PCM and EPS, perhaps include a wiggle test too.

Looking at CAN-nio there is most certainly a change to the voltage threshold of the CAN network but CAN Hi - CAN Lo still decodes OK at the correct thresholds of 0 to 2 V

Whenever we have voltage threshold deviation in CAN we must be mindful of the tiny current present in a CAN network (20 mA max) and just how vulnerable it will be to momentary changes in network resistance.

This will present itself as the disruption we see in CAN-nio or even deformed data packets. This post is a perfect example topic20981.html

Momentary CAN network resistance anomalies are generally caused by the node/ECU terminal pin contact, water ingress, corrosion, and chaffing, routing, previous harness repairs, movement or possibly contact issues at PCB level within a node.

I hope this helps and please feedback when you can, take care……Steve

terbo
TwoWaves
TwoWaves
Posts: 69
Joined: Sun Jul 06, 2014 2:40 pm

Re: Citroen C3 2007 loosing Power Steering

Post by terbo »

Thank you for the Tips.

We had a look at the Car again, and found two
Suspect Terminal Pins, we cut them off, replaced them with
new ones, plugged all together and now its on for testing.
Because we could not get it happening again.
I am not 100 % sure, that those two Terminals are all it needed,
but they were one CAN and one ground Line Pin.

Checked voltages, between the BSI and the EPS ECU with
the Scope, and could not see any time differences between
"Power Online" Time, but great idea.

We will see, i will follow up, when he gets back from
vacation, so long the Car is sitting in the Garage.

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