[Scrubnut]

When VW plug into the diagnostic port, can they tell if anything is wrong with the car even if there are no symptoms or does there have to be an obvious problem first?

 

[Privatedoc]

Fault codes are stored in the ecu so yes, they can detect problems , even if not apparent or intermittent

You can read these codes yourself with an obd2 scanner tool

 

[Scrubnut]

Thanks!

I see I can get one of these for about £20. If I did, would I know what was wrong or would I just get a list of random jibberish?

Sorry to sound like a numpty, but I think this is interesting and it would be good to turn up at the dealer and tell them what was wrong myself!

 

[ptae2000e]

Here is an illustration of what a list of problems looks like:https://lh5.ggpht.com/ps72wQBmIOJbFdADS88rs0ubrkK5ESOpBfOb6tinePsypUHtsAL8NfugPTOVVUsSyLU=h900. I don't know how extensive are error description if one would click on "more information" - I didn't have any problem codes when I've tried a reader.

Also note if you plan to leave the obd2 reader plugged in all the time, you'll need to obtain one specifically designed for that, otherwise they could empty the battery.

 

[Rickenbacker]

The codes are only a guide and do not always pinpoint exactly what the issues is.

 

[giggle pin]

OBD only scan tools only read the engine fault memory

Cheap scan tools can list stored faults incorrectly

A logged fault is only an indication of a potential problem area it does not list associated functions that may have caused the fault to log.

i.e: an Air Mass low fault could be issued due to an internal air leak or EGR valve failing - it does not mean the Air Mass meter is at fault.

That is why good workshops repair cars at the first visit & poor workshops replace the air mass meter and other components in what's known as the "parts shotgun" approach.

Professional workshops use scanners costing thousands of pounds with subscription fees running into thousands of pounds - £20 scanners are generally flawed.

VCDS is the best value value scan tool out there for VAG cars & is priced ridicuously low at the sub £400 mark.

hth




Edited by: giggle pin