I don't have a good multimeter for that measure, I will try to find a better one.

In the meanwhile, I found another way to "fix" the problem, before starting the engine, I remove the fuse n°7 in the fusebox ("Engine electronics, power-assisted steering" label name), next, I start the engine and the power steerig warning light is on that is normal without the fuse and finally I put back the fuse n°7 and everything is ok.

 

So, I don't know if there is something to check around that fuse ?

7 hours ago, ppetienne said:

... I found another way to "fix" the problem, before starting the engine, I remove the fuse n°7 in the fusebox ("Engine electronics, power-assisted steering" label name), next, I start the engine and the power steerig warning light is on that is normal without the fuse and finally I put back the fuse n°7 and everything is ok.

 

So, I don't know if there is something to check around that fuse ?

All that is doing is delaying when the PAS module is woken up (by the ignition-on voltage from fuse 7) and starts to read the local terminal 30 voltage it sees. That extra time will give the battery/system voltage a chance to recover after glow-plug and starter motor activity.  

That does seem to confirm that once it sees a good voltage at the ends of its thick, permanent 12V supply wiring, it is happy. Maybe try replacing that pair of wires with some harvested from a scrapyard car?

 

 

 

Yes, it is what I tought but if indeed it is what happens, for me the pair of wires of the PAS are good because there is any problem after a delay, so they are well providing the good voltage, am I wrong ?

You are probably right.

Something is causing it to sometimes see a voltage it is unhappy about, It could even be a problem internal to the PAS module that is pulling that voltage down more than normal.

 

Apart from re-checking the parasitic current, I've run out of ideas.

Replace the pump with a secondhand unit and see if the problem persists.

On 18/06/2021 at 10:58, AndyPandy said:

 You mean resistance of the cable,impedance relates to Alternating Current,Resistance relates to Direct Current.Because the cable you mention is a large copper core,the only way to measure its resistance would need a special instrument, using a multimeter  would not show any meaningful value.Puting it simply the multimeter  leads have a much higher resistance than the cable you are trying to measure. THe actual cable will not be faulty because of the amount of copper conducter used.The end connections as 'Wino' mentioned are where faults are possible. Possibly putting the multimeter leads on both ends of the cable,setting the multimeter on the low end of the DC voltage range.Then starting the car will give a reading,and comparing this reading to another car would be useful.

To be technically correct. Impedance is the combined effect of inductance and capacitance to the flow of alternating current. It's a subject for many hours of study, but not in the context of DC car electrics. I concur with Sep on this. The correct item under consideration is volt drop caused by high resistance joints. As a man(possibly OHMS)one said"when a current of one amp passes through a resistance of one ohm then one volt will be dropped". It only takes a bad connection at the battery or a battery with a high internal resistance to cause this sort of problems. The problem that modern day folks do not appreciate is that modern voltmeters read the battery, but with high resistance, so any current draw is minimal. What is needed is to check across each joint to look for volt drops. e.g. In a starter circuit, I'd expect to see no more than 0.5 volts drop across the solenoid. But tracing this sort of fault is a skill gained from many years of experience.

Agreed, very simple to do and definitive.

 

I should point out for anyone who uses a multi-meter but perhaps does not really know what is going on that the volt drop test has to be done with the circuit under full load, ie in this instance with someone else cranking the engine.

You could also log (with VCDS measuring blocks in module 44) the terminal 30 voltage at the PAS module during start-up, and compare with a car not showing such faults.

I can offer a comparison log from my Polo, but it won't be very comparable as mine has no glowplugs and lower compression, being a petrol engine.

 

Edit, it does however have an 8-year old battery that was mistreated quite badly early in life when installed in an off-the-road Mk2 Golf.

Edited 30 June, 20214 yr by Wino

Hi,

 

I could connect a VAG module (ODBeleven) and I got the follwing error:

00566 - Steering assistance operation - Implausible signal

And here is the information provided on the wiki for that fault code 00566 - Ross-Tech Wiki.

 

Unfortunalely, with that module, I couldn't perferm a measuring blocks in module 44 but I could perform a monitor of the ODB voltage and here is the graph when starting the engine:

 

I also performed a test by desconnecting all the fuses on the battery fuse box except the 2nd one ("Interior" fuse) to check if a main module was not consuming a lot of energy at startup but the result was the same, the voltage slew down to 9V ...

 

So, I suppose that it's the starter motor that is creating that voltage drop,  could be this the root cause of the PAS issue ?

 

Edit: I made the parasite current measure and I got 0,17A, I don't know if I waited enough time after having closen the car because that value seems quite high regarding your previous comment ...

 

No, it's probably the PAS pump motor rather than the starter that's pulling the voltage down.

Actually, I made a test without the PAS pump connected and I got the same voltage drop ...

1 minute ago, ppetienne said:

Actually, I made a test without the PAS pump connected and I got the same voltage drop ...

 

Then you have a rare electrical fault that we cannot diagnose from across the internet.

Good luck with it.

It's completely normal for the starter motor to cause a deep, brief dip in voltage measured across the battery. Nothing unusual about that. 

 

But the PAS module thinks there is more of a problem than just normal start-up behaviour, so we really need to know what voltage the PAS module itself is seeing during the early stages of operation. I don't think that is what your red line is showing, I suspect that is voltage at the battery as seen by the Onboard supply control unit, or in the engine control unit; whatever it is that your OBD cable is talking to.

 

How long did you wait when measuring the  parasitic current?  That 0.17 amps is much too high if that reading is correct.

 

I've just taken some photos and video to illustrate the technique that I described earlier in words, in case that hasn't been understood.  I'll make a post about it in a minute, and come back here with a link.

 

The 13.1 volts showing after the alternator gets going is very low, suggesting that the charging current into the battery is very high at that time, because the battery is in poor state of charge, or that the cabling from alternator to battery is losing voltage.

 

 

Quick and dirty parasitic current measurement - Handy Topics & Guides - BRISKODA

Hi,

I made again the parasitic current measure waiting at least 45 min after having locked the car and I got 0,06A but honestly I don't trust so much my multimeter.

 

On ohter part, I could retrieve data from the PAS module with the ODBeleven module:

• When the PAS is well turned on:

 

• When PAS is dectecing voltage issue:

 

The Value 4 of the channel 4 is the voltage read by the PAS ?

It seems that when that value is low, the PAS is not turning on.

I think both voltage figures are as seen by the PAS module, possibly one is the terminal 30 permanent feed, the other the terminal 15 ignition-on feed from fuse 7.

I will try to find more info tomorrow.

Great data! 

Hi,

 

After searching a while on the forum, I could find that :

 

So, the channel 1 - value 1 represents the voltage value of the terminal 30 and the channel 4 - value 4 represents the voltage value of the terminal 15.

 

Now, I don't well understand why those values are different and with a delay between them ?

I could see on others tests that sometimes, the terminal 15 is delayed regarding the terminal 30 and sometimes, it's the opposite ...

I think the time difference in the sampling will partly explain the differences between the voltages. They can't be measured truly simultaneously.

The other factor is the currents through the (non-shared) wiring will cause variable differences between the two voltages.

 

I'm shortly going to do some logging on my car.

 

See if you can make the PAS module start up reliably by not touching/moving the steering wheel during the first few seconds after engine start.

See if you can make it go into error condition by deliberately moving the wheel during this time.

 

 

 

 

I messed up this morning's logging, so here's a brief one I've done just now.  This was just logging group 1 and 4, as the current logged in group 2 is the same as in group 1 I think, so no need to look at that too.  Notable difference is that when the PAS starts up (with no steering wheel input yet), there is not the big current surge that is seen in your first plot, just a climb to the 'circulating fluid but not pumping hard' 3 amps standby situation.  You can see on the right what happens when I give the steering wheel a bit of left/right waggling while stationary on block-paving.

 

Maybe repeat your experiments to see if that big current spike happens every time the PAS starts up, even with no steering wheel movement.

 

 

 

Do you know if your car has the TRW steering system or the Koyo one? There may be differences in start-up behaviour.

Hi,

Thanks a lot for what you did !!

So, first, with or without moving the steering wheel at startup I have any difference, only once, the issue didn't occured when moving it a lot but I tried this trick again but without success ..

 

For the current peak, for me this doesn't  seem directly to be the root cause as when the issue ocurs there is no current peak. But maybe this is showing a PAS issue ...

 

I have the Koyo model (sesgo attached), what is yours ?

 

Mine's TRW. 

 

 

 

 

Hi,

 

Do you have any idea to go ahead ?

 

Many thanks

Find someone with a Fabia that also has the Koyo steering system and is willing to let you make some graphs of the voltages and current during the time when the PAS module is starting up in their car.  Then you can see if that large current spike is normal or abnormal.

All UK (RHD) mk1s have the TRW system, I think.