Audi TDI Diagnosis: 96 vs. 2001 - Why?

I have no idea about microelectronics. So, please don't be upset if I don't describe something correctly or if I don't understand an answer and have to ask again.

'Some time ago, I purchased a diagnostic adapter with VAGCOM interface for RS232 and based on a microcontroller. After initial excitement about the product, I quickly became dissatisfied. The only vehicle I could read data from was my 1996 TDI. When I tried using it on two 2001 Audi TDIs, no diagnosis was possible. The error message I consistently received was that a connection to the control unit could not be established.'

After searching the forum, I haven't really found anything helpful either...


Thank you in advance for any information you can provide.

Where did you buy it?
How's it going? / What's up? / How are you?

Sorry. I would not like to name the seller here. I ask for your understanding.

The interface connector is about the size of a matchbox, comes with a 1.5m RS232 cable, and even fits into the narrow compartments in the Passat and A4 (8D) models. The connector has 4 pins. That's all I know.

Best regards!

Hmm... how can I help you if you don't tell us what information we need?

Sorry, but you won't get any help like this.

The only conclusion is: buy or build a decent interface.

Well, I guess I'm out of luck. I got the tool from someone who's also active in this forum... That's why I'm not mentioning any names.

Thank you for offering your help, nonetheless.


I don't want to imply that anyone is incompetent or damage anyone's reputation. That is absolutely not my intention. Therefore... (This is purely for the purpose of understanding the causes!).


Best regards!

Hi,

at least in the diesel mechanic shop, there have never been interfaces with microcontrollers and only 4 pins in the OBD2 connector... that's all I have to say about that. The HEX-USB/HEX-COM, etc., always have all the pins in the OBD2 connector.
How can I help you if I don't know what hardware you have? Just ask your seller where the problem lies.

Best regards, Rainer.

Ich hatte mit dem Verkäufer gesprochen gehabt. Der kennt sich zwar mit Mikroele. aus, hatte aber von solchen Problemen auch noch nicht gehört. KA hunch!

I then looked around in the forum and read about frequent problems with optocouplers. After that, I mentioned the 'V' to him. He said that his product doesn't work based on optocouplers. That's why I assumed it used microcontrollers... I didn't really understand his explanation anyway. As I said, electronics isn't my area of expertise.



Best regards!

How about the rest of your hardware? Is everything in order?

If you're adding one and one together, you likely don't have an MC (Microcontroller) directly in the interface, but rather an interface converter like a MAX232 or something similar. Assuming everything is working correctly (PC, adapter), it should work. And if it's the adapter that I think you might have, it should also work.

I've done quite a few COM port tests and tried various settings. The connector works perfectly fine with my coffee machine, but it doesn't even work at all with newer Audi models.

Was für Möglichkeiten an Defekten gibt es denn für RS232?... Wie gesagt,es ist schon sehr verwunderlich,daß bei meiner 96er Audi-Mühle alles machbar ist. Seltsam !!


Thank you!

If you could open the interface and simply tell us the part numbers of the ICs (those small black components with more than three legs), it would certainly be easier to help. It would also be interesting to know if any potentiometers are installed (adjustable resistors that can be mechanically adjusted).

However, I suspect that you will ultimately need a "better" interface. Because yours isn't completely broken, but rather has limited functionality. In my opinion, this suggests a lack of quality rather than a defect.

Regards,
Guste.

I don't want to open this part because doing so won't be completely without consequences.

The seller offered me a replacement. I'll probably accept it.

To avoid future problems with this kind of equipment, I will follow your advice and, when my budget allows, I will probably purchase a decent professional diagnostic tool. Hopefully, that will spare me the trouble.

Thank you very much for your help so far in investigating the cause.


Best regards!