Some time ago, maybe in July, I posted somewhere within briskoda that after scanning wife's August 2015 Polo I had a "590081 - Control Circuit for A/C Compressor B10A9 11 [008] - Short to Ground   Intermittent - Confirmed - Tested Since Memory Clear ----"  then without me requesting that VCDS cleared these faults, the next time I scanned that car, probably weeks later, that logged fault code had vanished, at that time I was given answer which I probably did not fully understand, James@RRGRochdale , so sorry!

Then in September, I scanned that car and found I had a "5688 - Control Head for Multimedia System  B13C9 F2 [008] - On/Off Switch  Intermittent - Confirmed - Tested Since Memory Clear ----" then without me requesting VCDS cleared these faults, the next time I scanned that car, that logged fault had vanished.

 

So what is happening, is this VCDS making a decision about this and clearing these faults or is it the onboard controllers dismissing these faults after some time has passed and they do not re-appear?

 

It is just that I can't really understand the phrase "Intermittent - Confirmed - Tested Since Memory Clear"  - well at least the "Tested Since Memory Clear" bit is what I do not understand fully.

Edited 6 October, 20169 yr by rum4mo

So what is happening, is this VCDS making a decision about this and clearing these faults or is it the onboard controllers dismissing these faults after some time has passed and they do not re-appear?.

VCDS just displays the fault codes that the ECUs store internally, it doesn't clear them by itself.

 

The clue is that the faults are shown as Intermittent, if there are sufficient startups when the fault doesn't happen then the ECU itself can clear the fault if it's not a serious fault but more of an informative warning.

So that can lead to intermittent logged faults being invisible to owner/dealer?  I don't think that that used to happen with older controllers, so that was why I was enquiring where the "clearing" instruction was coming from.  I've always known that intermittent engine/emissions faults did bring on the relevant dashboard indicator and then let it go off if they did not happen frequently - but the reason of these indicators coming on remained stored in the engine controller until cleared by a scan tool.

 

Is this now a recognition that ghost/random fault conditions will/can happen and with time they will be considered irrelevant and so discarded?

 

What I find curious is, I've been able to view and print off both these faults, just in case they are relevant later on, and in each case the next time I've scanned the car, they have disappeared, so has this got anything to do with both of these controllers "knowing" that they have been scanned and so clearing irrelevant faults, or is it just pot luck that I've viewed them before they were cleared?

What Dave's saying is that non-critical intermittent codes like you cite are deleted from the ECU memory by the ECU if they don't occur more than once in $time. It has nothing to do with fault code readers.

Yes that could have the effect of making them invisible to you, but when you consider that something like a low battery can throw 20 codes there has to be some way of the ECU clearing memory without 3rd party action.

Well maybe, but at least the first one is a fault code that also inhibits the AC chiller when it occurs and there is a software update to stop that incorrect fault  code and effect happening, I kind of wonder what happens when someone gets frequent occurance of these faults but just fails to get the car booked in in time for the dealer to see that a fault code has been logged - so does not ever resolve an issue.

 

Rather makes a joke out of what started out as being  a smart way of handling fault locating.

Rather makes a joke out of what started out as being  a smart way of handling fault locating.

That's VW's choice, nothing to do with the developers of VCDS, OBDEleven or any other code reader :peek:

That's VW's choice, nothing to do with the developers of VCDS, OBDEleven or any other code reader :peek:

 

I think that I worked that out (after the first reply in this thread), it is just the way that FDLS seems to have evolved in VW group products that confused me.  I used plenty bits of kit, where for convenience and other constraints, only the past four faults in each controllers get kept before overwriting, so if you had only one intermittent fault in a controller, at any time, when interrogated that fault should always be seen as an event. That made sense as any operator that was continuously ignoring faults could not keep increasing the number of faults logged in a single controller. VW group's current way of doing things seems to have made a joke of that.

Edited 8 October, 20169 yr by rum4mo

If you look at the VCDS scan you will a number of figures.

 

Take this scan of the HVAC on my Audi A8, you can see multiple faults (an old scan by the way)

 

The key to look for is reset counter, if the fault has this associated then following that number of drive cycles the fault is automatically deleted. Should the fault reoccur during the countdown the valus is reset. The reset value is ECU and fault dependent, different faults have different reset counts.

 

Address 08: Auto HVAC        Labels: None

   Part No SW: 4E0 910 043     HW: 4E0 820 043 

   Component: KLIMAAUTOMAT    016 0240  

   Revision: 00000020    Serial number: 00000000024718

   Coding: 1069297

  

 

6 Faults Found:

00065 - Left Rear Footwell Heater (Z42) 

            004 - No Signal/Communication

             Freeze Frame:

                    Fault Status: 01100100

                    Fault Priority: 3

                    Fault Frequency: 1

                    Reset counter: 197

                    Mileage: 228864 km

                    Time Indication: 0

                    Date: 2015.06.15

                    Time: 21:33:15

 

             Freeze Frame:

                    Voltage: 13.90 V

 

01087 - Basic Setting Not Performed 

            005 - No or Incorrect Basic Setting / Adaptation

             Freeze Frame:

                    Fault Status: 01100101

                    Fault Priority: 2

                    Fault Frequency: 1

                    Reset counter: 197

                    Mileage: 228864 km

                    Time Indication: 0

                    Date: 2015.06.15

                    Time: 21:32:01

 

00066 - Right Rear Footwell Heater (Z43) 

            004 - No Signal/Communication

             Freeze Frame:

                    Fault Status: 01100100

                    Fault Priority: 3

                    Fault Frequency: 1

                    Reset counter: 71

                    Mileage: 235633 km

                    Time Indication: 0

                    Date: 2015.10.03

                    Time: 14:06:09

 

             Freeze Frame:

                    Voltage: 12.80 V

 

02021 - Supply Voltage for Heating Element in Right Rear Footwell 

            002 - Lower Limit Exceeded - Intermittent

             Freeze Frame:

                    Fault Status: 00100010

                    Fault Priority: 3

                    Fault Frequency: 81

                    Reset counter: 105

                    Mileage: 228873 km

                    Time Indication: 0

                    Date: 2015.06.18

                    Time: 12:36:47

 

             Freeze Frame:

                    Voltage: 12.90 V

 

00716 - Air recirculation Flap Positioning Motor (V113) 

            003 - Mechanical Failure

             Freeze Frame:

                    Fault Status: 01100011

                    Fault Priority: 3

                    Fault Frequency: 145

                    Reset counter: 77

                    Mileage: 228866 km

                    Time Indication: 0

                    Date: 2015.06.16

                    Time: 17:43:47

 

             Freeze Frame:

                    Voltage: 12.70 V

                    Temperature: 34.0∞C

                    (no units): 43.0

                    (no units): 7.0

                    Temperature: -76.0∞C

 

01844 - Control Module for Fresh Air Blower (J126) 

            004 - No Signal/Communication - Intermittent

             Freeze Frame:

                    Fault Status: 00100100

                    Fault Priority: 3

                    Fault Frequency: 29

                    Reset counter: 112

                    Mileage: 228992 km

                    Time Indication: 0

                    Date: 2015.06.26

                    Time: 17:18:32

 

             Freeze Frame:

                    Temperature: 25.0∞C

                    Speed: 100.0 km/h

                    (no units): 170.0

                    (no units): 145.0

Yes, legacy controllers will behave like that I think and that record will remain in that controller until reset manually, what I have been finding, with latest controllers is, while "first occurance" "priority" "reoccurance" etc etc  are still being logged, after a few engine starts without this fault re-occurring, the complete record, as far as VCDS/Carista are concerned is getting wiped, so as far as I or the dealer is concerned, they never existed and the fact that I have been lucky enough to "catch and print" them will mean nothing - and the first one I found is a known software issue which does cause the AC chiller to be inhibited and which will only get addressed if the dealer can see it, and the chances of that tend towards zero.

 

For me this is completely different from stupid wrong fault codes appearing as they tended to do in the past, ie "bank 2" issues in a straight 4 engine - again a known software issue that if they could be bothered, my VW dealer would have known about and corrected which would have avoided me needing to clear these rogue faults when the fault light used to come on, typically in winter, on my wife's previous Polo.

 

I don't want to go on and on about this, but maybe I am one of the few VCDS users that are "bumping into" these faults on newer cars.

 

One other thing, if no one has noticed/discovered, current EVAP systems seem to have a new fault code number, VCDS and Carista can translate it correctly or give the same description - but I can't find that code listed anywhere including the RossTech Wiki site.