mk3 golf OBD port

[mick01]

In my 1997 mk3 golf 1.4 AEX engine code, there is the 16 pin OBD port beside the ash tray, connecting a basic fault code reader to it says "no connection", am I to assume this model is not OBD compliant? Also, what's this vag.com stuff all about, some form of diagnostic tool? if so, where do you get it from , is it any good, and would it work on my model of Golf, or do I have to rely on good old fashioned mechanical knowledge?

[Doctle Odd]

Basic OBD reader would be of little use, this would work it's the basic version of vag.com now called VCDS. What's wrong with the car?

http://www.gendan.co.uk/product_VAGUSB.html

[mick01]

Hi Doctle odd, and thanks for your brief reply. Only problem at present is the Mot emissions test which its failed twice with consistently high CO reading at high speed but not at idle. Can post readings if they make any sense to you? So far iv changed the lambda probe for a new one, Engine temp sensor (for a known good one), new air filter, plugs, oil etc, put some fuel cleaner in the tank, a high speed run prior to the mot test and again it failed, cat would be the next thing (by elimination), as the present one is aprox 3 years old and an after market one, so it may well be passed its best as it struggled to pass emissions test last year, but just scraped through. The car runs very well, is well maintained and good on fuel. I thought an OBD reader would highlight any problems, iv tried two OBD readers and both say "no connection". Im a competent home mechanic but never worked on OBD's before and not a computer GURU (computers weren't about when I was at school). so im intrigued by this VAG.COM idea, I saw your link to the connection lead, but what then? do I have to down load some soft ware, where from, is it free or expensive, how do you use it, is it any good and would it work on my car. Any advice you can tender is very welcome as im breaking new ground here. Thanks again.

[Doctle Odd]

Are there any leaks however small in the exhaust? If you replaced the lambda for a genuine one that just leaves the cat. VCDS (vag.com) requires a computer usually a laptop and the diagnostic cable. There is a free diownload of the software available from the developerwww.rosstech.com. The high readings suggest a leak/lambda/cat

[mick01]

No major exhaust leaks, one very minor one rearwards of the lambda and cat, so that shouldn't affect matters. Its a one piece down pipe which houses the lambda probe then a flange joint (leak free) straight into the cat. I'm lead to believe a high CO figure indicates a rich mixture (is that correct) ? So probably it is the cat, as iv changed all the other possibilities, or perhaps excess crankcase vent fumes entering the inlet air box would cause a rich mixture (but unlikely). Iv got the laptop so ill check the software you have mentioned, if it downloads ok ill go and purchase the connecting lead, but will that set up VCDS work on my age and model of car? Thanks for all the info.

[Doctle Odd]

Here is a link to the application data list for a 1996 Golf. It really doesn't cover a lot on those cars. If you don't have the CEL or check engine light on then your car isn't picking up on the fault. Is she a single point injection for the fuel? The unit could be over-fuelling. Is everything tight on the intake side of the engine ? To be honest VCDS won't do much for this car it relies more on old school diagnostics, here's the link anyway Ross-Tech: VAG-COM: Golf / Jetta Applications

[mick01]

Hello there, mine is a 1997 model, anyway, no leaks on the intake side every thing seems tight, and no warning illuminations on the dash, I don't even know if there is an engine "check" or warning light fitted on this model. Its a multi point injection system and again every thing seems ok. I will check the link you have posted later on and see what it says, but if VCDS wont work on this car then yes its down to old school diagnostics. My thinking is - the lambda probe measures oxygen content in the exhaust gas, and then alters the fuelling to the point where there is NO Oxygen in the exhaust gas thus ensuring a complete burn of the fuel, so there for any excess crankcase or fuel vent canister fumes entering the air box would effectively be burnt, (is my thinking correct) ? Also the plugs are a good colour, but exhaust tail pipe a little sooty black, which tends to indicate a rich (ish) mixture. Also I believe, the cat should absorb some of the by products of combustion, namely CO (carbon monoxide) and if as I suspect the cat is buggered, this would give a high CO reading at the tail pipe. I chatted to the mechanic at the MOT place about this problem and whilst a pleasant chap he didn't know any more about the problem than you or I do. Thanks again, I will check the link posted and report back to you.

[Doctle Odd]

The data is the same for 1997, most of the OBD modules are for air-bags, ABS etc. Maybe you should ask Crasher of Zollaf of this parish, both are experts. I'm thinking CAT but it's a considerable expense especially if the diagnoses is wrong. Is there an EVAP cannister?

[mick01]

Yes there is an EVAP canister in the drivers side inner wing, not sure if that would have any bearing on the matter, as any vapour would be inducted by the engine and burnt and thus monitored by the lambda probe, ( or am I mistaken?) and yes a cat is expensive, hence (trying to save some money) by reading the OBD system if that's possible on this model. I checked the link you posted and the engine is one of the modules monitored, but whether that includes emissions I don't know, I didn't see any free download software on that site either. Any thing else you can suggest is most welcome. Thanks again.

[zollaf]

post the results.