Power steering electrical circuit

Bordos

Member
Poland
Hello,

As I need to do some troubleshooting regarding the power steering in my A2 I would need a circuit diagram for electrical system of it - if anyone have it I will appreciate sharing it with me.

Thanks.
 
Welcome!

Can you describe the symptoms of the steering problem you are encountering?

Are there any other salient criteria you can think of - is this a sudden development contingent with local cold weather, are you encountering any other problems indicative of low battery charge, other error lights etc. ?

Is your air conditioning functional?

I don't have a circuit diagram - there are others who may be able to share this with you fairly quickly once they see the thread - but giving us some more information as above and anything else pertinent will help with the assistance we can give.

Very best of luck!
 
The "Steering Fault" is activating only from time to time and usually just for a moment (I get a "beep" and the fault, but the steering is fine and the fault clears immediately) - it stayed longer only a few times (with the steering assistance gone).
I happens while maneuvering in standstill or almost standstill and while maneuvering on bad road surface - therefore I reckon that in those conditions the steering HPU motor require more power (hence more amps) to operate and maybe some earth connection/supply wire is staring to develop bad contact.

VCDS diagnosis shows no faults regarding the power steering.

Air-con is working just fine (but as it is winter I do not use it very much).
 
I think you are lucky then compared to other steering failure possibilities.
This sounds like a transient low voltage / high current drain issue. How fresh is your battery - and have you recently experienced low temperatures? Are there ever any signs that the alternator is not giving full output? There are a series of voltages you can record using VCDS - before the engine is switched on, while cranking and when the engine / alternator are running being those that I can think of. Then also when adding drains such as the headlights, heated rear window etc. Between these pieces of information it may be possible to diagnose a dying battery or alternator that needs to be renovated that are contributing to your symptoms. Cold weather can also cause voltage drop in the battery, so similar questions tend to appear at A2oc every December!

As you know the steering has a huge electric pump that drives the circuit. Just after you have started your car, if the battery is already losing potency, sometimes the demand of driving the pump as well as other electrical demands on the alternator can already be seen on dark days by the headlights being dimmed as you turn the steering wheel. If the voltage is sufficiently low that critical safety circuits can be impacted, devices that are less important are temporarily inactivated - and anecdotally I've picked up here that the steering assistance can be temporarily part-suspended as part of this when the battery is very weak.

This sounds like your problem - so I would start by looking at the battery and then the alternator. It is not uncommon to find the battery is a VARTA with an 8Z0 code on top - original from the factory batteries at 20 years old like this are still seen reasonably frequently although only because it is now time to change them as they are beginning to die from old age.

Very best of luck!
 
As it is winter time -10 C is not something new :)

It might be caused by the battery, but as it happens regardless of outside temperature therefore I will start by checking the earth connection and measuring voltages.
 
The "Steering Fault" is activating only from time to time and usually just for a moment (I get a "beep" and the fault, but the steering is fine and the fault clears immediately) - it stayed longer only a few times (with the steering assistance gone).
I happens while maneuvering in standstill or almost standstill and while maneuvering on bad road surface - therefore I reckon that in those conditions the steering HPU motor require more power (hence more amps) to operate and maybe some earth connection/supply wire is staring to develop bad contact.

VCDS diagnosis shows no faults regarding the power steering.

Air-con is working just fine (but as it is winter I do not use it very much).
The description above points me in the direction of the 30 amp power steering fuse, or the supply to and from it. Check the fuse box in the footwell (passenger side in RHD, not sure about LHD), and the connections to it. It sounds very like voltage drop across a high resistance connection. The power steering dears a very high current, so connections must be clean and bright, and tight.
Mac.
Edit: Corrected LHD & RHD.
 
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Maybe I need to visit the opticians?
Very high current then. Wouldn't need much resistance to drop a few volts.
Mac.
I'll put the opticians off for now, here's where 30amp came from, I'd assumed the (30) meant 30 amps. So eyesight is OK, but thought process, maybe not so much.:
Screenshot 2023-01-02 16.52.46.png


Mac.
 
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Also check the connection between the fuse, the power steering module (J500), and from the power steering module to the power steering pump
itself, as these all carry the high current supply.
Mac.




Screenshot 2023-01-02 17.41.28.png
 
Too little or too much fluid in the pump will also have and effect as would the wrong fluid. The wiring connections on the pump can corrode so that would be an area to check really carefully.
 
Also check the connection between the fuse, the power steering module (J500), and from the power steering module to the power steering pump
itself, as these all carry the high current supply.
Mac.




View attachment 102789
Can you show me the bottom part of this diagram - I hope to see the reference to which earth point is connection T2e/2 connected ...
 
I have been having very similar issues with my 1.6 FSI last few weeks , seems to definitely be battery related as after charging battery it seemed to be OK. Weather dropped again last night and once again issue is back, plus I now have alternator / battery discharge warning illuminated . I suspect Alternator or earth , then battery . But will update as I have time to troubleshoot. Currently after the last occasion when I had the steering warning on DIS at startup I havent had a chance to look at or troubleshoot. Would be very interested in finding out what maybe root cause , and will update if in meantime I get further with mine
 
Too little or too much fluid in the pump will also have and effect as would the wrong fluid. The wiring connections on the pump can corrode so that would be an area to check really carefully.
Have checked fluid level in the reservoir below the NS headlight . All seems ok. I do need to check connections for corrosion and confirm Earth is OK too.
 
The pump motor itself could be failing. The power steering pump is by far the largest consumer of power and will have problems from the simplest thing to the most complicated. All connectors need to be corrosion free and tight. The battery and all the connections to it including the auxiliary positive box must also have clean contacts and be tight. The fluid level must be correct in the pump and its connector clean and tight. The main earth lead from the starter to the chassis under the left headlight must be perfect- can be clean and tight at either end yet corroded or broken under the insulation. The alternator and charging system must be working correctly. The fuse must be good, clean and no signs of burning......
 
The pump motor itself could be failing. The power steering pump is by far the largest consumer of power and will have problems from the simplest thing to the most complicated. All connectors need to be corrosion free and tight. The battery and all the connections to it including the auxiliary positive box must also have clean contacts and be tight. The fluid level must be correct in the pump and its connector clean and tight. The main earth lead from the starter to the chassis under the left headlight must be perfect- can be clean and tight at either end yet corroded or broken under the insulation. The alternator and charging system must be working correctly. The fuse must be good, clean and no signs of burning......
About the earth point - are you referring to the one that starter motor is connected to?
If so - the power steering motor is not connected there.
 
The pump motor itself could be failing. The power steering pump is by far the largest consumer of power and will have problems from the simplest thing to the most complicated. All connectors need to be corrosion free and tight. The battery and all the connections to it including the auxiliary positive box must also have clean contacts and be tight. The fluid level must be correct in the pump and its connector clean and tight. The main earth lead from the starter to the chassis under the left headlight must be perfect- can be clean and tight at either end yet corroded or broken under the insulation. The alternator and charging system must be working correctly. The fuse must be good, clean and no signs of burning......
Yes I need to check the earth from starter to under headlight, then alternator ... then take it from there ...
 
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