Just hoping someone can give me a hint on this one. Car is a '59 plate Fabia Estate 1.9Tdi with just on 100k. I've only had it for two months & the power steering has never given any sign of trouble until last Saturday when I drove it about 4 miles (everything fine), parked it, then when I restarted it, no power assistance & the warning light on the dash. When they say the steering will be heavy that's a big understatement! Anyway, I did a VCDS scan with the following fault codes coming up :-

Steering Fault Scan.txt

 

 

 

 

 

         I checked all the fuses (all o.k.) then proceeded to rip the front off the car to get at the offending article. The large 12v feed for the motor was fine as was the large earth return. On the three-wire plug (on the left of the pump looking from the front) the 12v ignition-switched feed on terminal 4 was o.k. All the connections on the plugs & sockets on the pump look clean with no sign of water damage.

         Now this is where I am lacking information as I've only got the wiring diagrams in the Haynes manual which, as has been pointed out before, don't show anything to do with the power steering, ABS, or airbag systems. However I am guessing that the brown wire coming from terminal 1 on the left hand plug is an earth connection. Am I right? If it is, then it's showing a very high resistance (300Kohms) between the plug & battery negative. Could this be the reason for 'no communication' with the power steering module? Incidentally, I did an auto-scan when I first got the car & there were no communication problems with module 44 & no fault codes shown.

         I hope someone can give me a clue on this as I'm reluctant to get another pump only to find the fault is elsewhere.

Not an earth, and not pure brown according to the wiring diagram I'm looking at.  Pin 1 is orange/brown, pin 2 orange/black?

These are the two wires that form the CAN connection to/from the PAS module, and as such are prime suspects for 'no comms' faults.

 

With a little more disassembly, you could check continuity of those two from that connector of the loom to pins 7 &8 of the instrument cluster's 32-way connector, or pins 3 & 5 respectively on a black 16-way connector going to connection labelled XS6 at the J519 Vehicle voltage control unit above the accelerator pedal.

Not sure which pair of connections is easier to get to on a mk2.

Many thanks Wino.

I guess the wiring colours fade a bit after 10 years. Looks like it's time to tear the inside of the car apart now. Hey-ho!

Have a look above the accelerator pedal first.  It's got a big piece of trim covering it in a mk1, but I have a vague feeling it may be more accessible in a mk2?

 

3 hours ago, Wino said:

Have a look above the accelerator pedal first.  It's got a big piece of trim covering it in a mk1, but I have a vague feeling it may be more accessible in a mk2?

 

Thanks. Will contort my feeble body down into the footwell in the morning whilst muttering 'gentle oaths'. Will let you know the results.

       Access to the Voltage Control Unit is reasonably good: no trim to move & just two very non-original looking tie-wraps to cut off. And when the unit is dropped down for access, what is written on the back in very 'car breaker' white marker pen - 'Seat Ibiza 2008'. I think this car has had an interesting history.

       Anyway, checking the two CAN control wires at the Voltage Control Unit plug showed them have continuity, although the resistance on both wires was 60ohms, which I would have thought to be rather high.

       Unless there are any other suggestions I suppose the only conclusion is that the pump module pcb is dead. Time for a replacement pump methinks.

I'm not sure from what you've written whether you've checked correctly.  You need one very long extension wire from one of your meter probes connected to pin 1 of the PAS module loom connector, the other to pin 3 of that 16-way at the VCU, expecting close to zero Ohms on a resistance range. Then from pin 2 at the PAS module to pin 5 at the VCU.  That would confirm that each of the two CAN wires is intact between these two control units.

 

Edit: just thought of a much easier strategy to test them both at once.  Disconnect the loom connectors at both ends.  Link pins 1 and 2 at the PAS end, then measure continuity between 3 and 5 at the VCU connector.

 

Edited 13 February, 20206 yr by Wino

I checked it exactly as per your first paragraph. I even checked the resistance of the long length of wire I used (which was a miserly 0.3ohms). However, I will recheck in the morning using your suggestion of bridging one end but I think I will do the bridge at the VCU end as it's less hassle to do the measuring at the PAS end.

     Checked the wiring with a bridge between pins 3 & 5 on the VCU plug & resistance check between pins 1 & 2 at the PAS plug. Result - 0.7ohm - all o.k.

     I think I know what was going wrong with my first measurements. I used a steel dressmaking pin to connect the meter lead at one end & I think it must have set up a 'dissimilar metals' cell which threw the readings out. I used copper wire only for the bridging & PAS connections this time.

    Anyway, looks as though it has to be the pump.

I might be interested in doing a post mortem on the pump  if it does turn out to be that (which it looks like).  I'd obviously pay you postage.

PM me if you have any interest, once your car is fixed, please.