fabia mk1 power steering warning light on again !

[turtlepower]

hi everyone

well here we go again ! having replaced the steering angle sensor some months ago on my 2001 1.9tdi fabia everything has been fine since until a week or two ago when the power steering warning light once again came on from start up and wouldn't go out by turning the ignition off and back on as it used to when the angle sensor was faulty

so I drove the car about 10 miles with the warning light on ,parked it up for 20 mins then when restarted it went out and stayed out for a week or so ,then one morning it did it again and I got friend to hook it up to vcds which said no communication with sensor or pump ,then a few minutes later it was working fine again and light went out

a couple days ago I went to start it and once again warning light on and now on permanently ,power steering still works but maybe a little less at low speeds if anything

things ive tried

vcds - no communication with sensor or pump ( everything else is communicating fine )

had battery checked at garage ,all good but decided to recharge anyway

tried a known good battery just to be sure - made no difference

alternator tested all ok

tested connecters to steering pump - main live and earth working fine ,live from cars internal fuse box ok and no blown fuses

removed and reseated all earth cables

 

I don't know how to test the 2 data cables that are on the socket with the live feed from the ignition to the pump so if anyone can help explain how to do this it would be much appreciated as I believe if one of these is damaged it would cause the communication issue

other than this I guess it would point to the pump ecu ? but as I said the power steering still works so pretty confused

any help or ideas would be appreciated

thanks

Edited 5 May, 2016 by turtlepower

[sepulchrave]

The pump is dying, the PAS works at reduced efficiency then finally stops altogether, chuck another pump on it before it packs up completely.

[Tech1e]

There is a known issue with the CAN data wires under the battery. Another member had this recently. You can check CAN communication with VCDS (Gateway 19, measured values). Worth having that up and moving the wiring about, see if the status alters.

[turtlepower]

thanks guys

ill get that checked and get back with the results ,do you have any idea where the the CAN wire connects up to at the other end from the pump ? as in is it possible to unplug both ends and test for continuity of the wires ?

thanks again

[Breezy_Pete]

I'll have a look.

[Breezy_Pete]

Those wires originate at the onboard supply control unit above the accelerator pedal, but there are a number of places where they join other CAN wiring, which may be easier to get to. For example, the CANH wire, orange/black at the 4-way connector on the PAS module should have continuity to the orange/black wire on (pin 8 of) the 32-way connector of the Instruments module (clocks unit). The CANL orange/brown wire from the PAS should have continuity to pin 7 of that same 32-way.

Edited 5 May, 2016 by Wino

[turtlepower]

that's great thank you

do the CAN wires play a part in the control of the the power steering ? as in ,if one of the wires is damaged does that prevent the power steering working correctly ? or is it possible to have a warning light because of a faulty wire but the actual steering is unaffected if you see what I mean

thanks

[Breezy_Pete]

The CAN communications from the Instruments module tell the PAS module what the road speed is, which affects the level of assistance specified (the slower you're moving, the more assistance). Comms with engine ECU are probably only to enable the PAS after engine start-up, rather than it being just powered up with ignition.

[turtlepower]

ah I see thanks

is the 32-way connector of the Instruments module easily accessible ? I presume somewhere around the steering column area ? 

thanks

[Breezy_Pete]

Plastic trim piece above steering column pulls off towards you, revealing two torx (T20?) screws holding clocks in. Remove those and the clocks are loose, connectors on back.

[turtlepower]

thanks again wino ,I will check these wires asap and report back results

[Breezy_Pete]

If you prefer not to pull out the clocks, the connector in question on the Onboard supply control unit is about the most accessible of any of them.  Footwell trim panel has to come off as if you were trying to get at the brake pedal switch (bottom left in the image below). The blue arrowed connector T16a (XS6) has a few CAN wires going into it (the ones inside the blue ring I think).  The ones you want to buzz through to are pin 5 for CAN-H (org/blk) and pin 3 for CAN-L (org/brn).

 

[turtlepower]

brilliant ! thanks wino, I will have a go at this today

[turtlepower]

ive taken it apart and tested the 2 wires back to the socket in the photo and the orange/brown is working but the orange/black is dead ,so ive traced this wire back to under the battery tray and cut it then made a temporary wire to connect back to the socket under the dash and lights gone out :clap:

is there an easy route through the bulkhead to put in a new wire

thanks again

Edited 6 May, 2016 by turtlepower

[Breezy_Pete]

That will be the problem, I'm sure.

It may be slightly more involved than running a new wire, because I think part of the CAN specification is that the wires are twisted with each other, at a specific turns-per-distance rate. So ideally you'd find the break in the existing run and mend it, or replace both wires from a point where they're 'known good' to the PAS module, with suitable twisting.  The latter might be a bit of a ballache TBH. and possibly non-essential.

 

It would be interesting to see whether a bypass wire without any twisting actually solves your problem, as an interim measure. The twisting together will be a noise immunity and impedance matching precaution that may be more of a nicety than an essential. Try it with a wire flown round through a window or anywhere, and see if communications are re-established?

 

Edit: Might be worth asking Tech1e (or searching the forum) for any more specific details of where previous members have traced the problem to? I guess 'under the battery' will be the starting point for a visual check, but that is a slightly different position from engine to engine.

Edited 6 May, 2016 by Wino

[turtlepower]

getting fault code 00778 steering angle sensor 49-00 no coms

01324 control module for all wheel drive no coms - not sure what this is but I seem to remember its always come up with this

no longer getting a no coms on the pump and warning light is going off

should I rig up a temp wire and use it like that for now or would it be better to leave that wire disconnected for now - will driving it without do any damage ?

is there a method to find where the wire is broken or better to just replace both with correct twisting ?

thanks

Edited 6 May, 2016 by turtlepower

[Breezy_Pete]

getting fault code 00778 steering angle sensor 49-00 no coms

01324 control module for all wheel drive no coms - not sure what this is but I seem to remember its always come up with this

no longer getting a no coms on the pump and warning light is going off

should I rig up a temp wire and use it like that for now or would it be better to leave that wire disconnected for now - will driving it without do any damage ?

is there a method to find where the wire is broken or better to just replace both with correct twisting ?

thanks

Have you added any bypass/repair wiring, or is that just the latest scan result with everything as it was?

 

I don't think you'll do any damage whatever you do, you just may get less steering assistance than you might get if everything was talking to everything correctly.

 

As far as finding the wire break, other than visual inspection and/or stabbing a fine needle (connected to a continuity meter) through the insulation at various points along the length starting from a point with good continuity, I dunno.

[sepulchrave]

getting fault code 00778 steering angle sensor 49-00 no coms

01324 control module for all wheel drive no coms - not sure what this is but I seem to remember its always come up with this

no longer getting a no coms on the pump and warning light is going off

should I rig up a temp wire and use it like that for now or would it be better to leave that wire disconnected for now - will driving it without do any damage ?

is there a method to find where the wire is broken or better to just replace both with correct twisting ?

thanks

 

Your ECU may be incorrectly coded, the 01324 error suggests this.

[turtlepower]

thanks guys, well I traced the dodgy wire back as far as where it goes next to the abs unit and each time I cut it back the piece that came off was completely corroded and fell to pieces in my hand so this is definitely at least part of the problem , so ive made up a temp bypass wire for both can wires from the steering pump right back to the connector in the photo ,I tried cutting the wires coming from the connectors under the dash and connecting the bypass wires directly to them but then there was no life in the steering at all and no check or warning light either so I reconnected the wires under the dash and added the bypass wires as a piggy back  

check light for power steering now comes on as it should before going out and steering feels how it should ,

still getting the same fault codes as above but originally I also had one for the power steering pump and of course the warning light so made some progress

[TMB]

The fault codes won't go unless you clear them.

[Breezy_Pete]

Good work fella.

[Breezy_Pete]

I believe there are some wiring junctions behind the dash where the wires from pins 3 & 5 of that connector meet up with the CAN wires from all the modules that use CAN comms. So, as you found out, those two don't *just* go to the PAS module.

[turtlepower]

thanks wino I really appreciate all your help its been of great assistance

and thanks to everyone else also

hopefully ill be able to get some miles under my belt before anything else goes wrong with it !

[Breezy_Pete]