Hi Guys,

I'm a new member, but long time Octavia vRS owner.

After 5 years and 45,000 miles of trouble free motoring, I'm having some issues with the ECU, but it tends to reset the fault codes before I can get it to some one with any diagnostic equipment. Sadly the problem usually crops up just before I'm due to go away, or during a long bank holiday weekend, such as this one.

I am therefor looking to buy a connection lead + software to run a diagnostic check as and when this on going intermittent fault happens again. I've been trawling through the forums here and there appears to be a lot of good information, but I have no idea what any of the abbreviations mean and consequently have no idea what is being said. VCDS, VAG-COM etc... Can some one please,please enlighten me?

While I'm here, can any one please recommend a lead/software package for a 2004 MK1 Octavia vRS and where I can get one?

many thanks,

VCDS and VAG-COM are one and the same.

Have a look here.

For a Mk1 Octy you can get away with a cheap ebay cable and the free version of VCDS.

BTW, codes don't usually reset- some do, but only after several succesful start/stop sycles, but most should stay.

If it's just for reading / clearing codes (e.g. you don't want or need realtime data or coding of control units) then a £39.99 delivered VAG + EOBD scanner off eBay will talk to the engine control unit, the ABS control unit, Auto transmission control unit (if present) and the Airbag control unit. This has the benefit of also doing just EOBD (reads engine control unit only) on other makes. Also they're a doddle to use.

If you just want to read the engine control unit any old EOBD scanner will do, they start at around £20 delivered and are just as easy to use but i reckon the ability to query ABS is worth the extra £20.

A computer based package will do everything (read & clear codes, coding + adaption, test procedures like activating ABS pump, real time data readouts & graphs) and it's fair to say VCDS (formerly VAGCOM) is the leading package.

Hope it helps!

Thanks guys, very helpful. They are a lot cheaper than I imagined!

When I say 'reset', my understanding is that when the engine warning light goes out, it means it has cleared the fault.

Or so a main agent has told me... after a hole mysteriously appeared in my lower radiator hose preventing them from running a diagnostic check. But thats a whole different story.

The engine light only illuminates when an emissions related fault is logged. The light may go out on its own accord, if after so many driving cycles the fault has not re-ocurred. The fault should still be logged as intermittent, sporadic or historic and will not disappear completely until it is erased, though sometimes they can disappear completely on their own.

Thanks for that Fordfan, I was begining to suspect the problem had something to do with the lambda sensor. I am looking to invest in a VAG COM type thing to interrogate it, as both garages are telling me different things, neither of them able to extract an error code.

Also know that while an EOBD device will report EOBD related fault failures, many engine faults in VAG cars will not be reported. The designers of the cars stick strictly to the minimum required to meet the standard. All other faults are only reported under the VAG specific protocols which can only be retrieved by a tool that reads the VAG specific codes. EOBD will be a subset of the codes.

Case in point: 2001 Audi TT no start condition. EOBD fault codes: 0 codes reported. VAG fault codes: 18 codes pointing to a failed relay.

When the MIL light is on, most often there will be EOBD codes. My point is that there may be other VAG codes that may lead you to a quicker and more correct repair.

And for the record, VAG-COM stands for VAG Communications and VCDS is VAG-COM Diagnostic System, the name VW allowed us to use when they pitched a hissy fit over the use of the letters VAG in the original product. So rather than fight with them in court, we changed the name. Same product. VAG-COM is now officially closed as a name. VCDS is the official name of the product.

Edited 9 April, 201016 yr by bearthebruce