C5 HDI 2L Power Steering Problem fixed

[Lale]

Thanks
Hi,
I am writing from down under so my approach could be upside down but I feel that my experience could be beneficial to others.
My C5 developed intermittent PS failure first which in the end become permanent. Checked what I could, eventually found mega fuse 80 Amp thanks to this forum as is hidden under fuse box and measured OK (Car manual is misleading as shows PS pump fuse in fuse box which is I believe for control voltage). Decided to seek help from a Citroen Dealer.
Suggestion was that pump is faulty (A$1500) + labour. Did not want to spend so much and found same pump on e-bay UK which arrived in four days.
Removed my pump and checked on loom connector for 12V which was there. Tested both pumps side by side. You need only +/_12V to two pin connector and +12V control on pin 7 on multi pin connector. To my surprise both pumps behaved identically where they would start on applying control 12v but would stop after 3-4 seconds. Realised by voltage monitoring that I was using not enough thick wires and on start up voltage would drop and pump brain would decide to stop. Replaced wires and bingo, both pumps were working fine. Checked other two pins 1 and4 and found with an oscilloscope the rotation confirmation pulses which are send back to BSI. It was clear that my pump is ok and suspected that somewhere on the main 12v path must be a loose connection. To confirm this produced an extension cable for main 12v supply to be able to measure voltage on ignition on. Theory was confirmed immediately. Search for loose contact revealed bad contact at the bottom of the fuse socket (unreachable). Decided to cut outgoing pump wire and connect via inline fuse (used for megawatt amplifiers in cars) to solid 12V bolt in the fuse box.
Sorry for a long story but might help someone.
Ah, just remembered to add that I have a surplus PS pump.

[Monkeyfeet]

Well done, must be pretty satisfying to get to the bottom of something like that.
Good post for reference too.

[degut94980]

Hello. Thank you for sharing your experience,but may you still remember what is that cable?
As I have same issue. But PS pump get +12v. In all connections all fuse also lools good and I don't know where I need to see more. Have message on dash power steering faulty.

[Paul-R]

What year/model C5 is this?

[degut94980]

2008. 2.0hdi. Saloon.

[degut94980]

I just checked more closer and I see that on 2pin big cabels I have about 14v (engine runing). On 5pin plug there just 3 cables brown,green and red.
Brown have 14v
Green about 2.36v
Red about 2.5v.
And lexia can't communicate with PS pump ecu.
But trough bsi it show fault code p047 (fault absence of communication with electronic power steering ecu). I also changed PS pump and no lucky.
Thank you