Diagnosis Interface Problem: Troubleshooting Guide

Good evening.

'I'm having a problem with the diagnostic interface. A colleague built the new circuit from www.dieselschrauber.de here at the company. It looks really great. The LEDs indicate that there is power from the vehicle (Polo 2f) and power from the PC. Also, the LED test in VAG COM runs without errors. However, the PC doesn't recognize the interface. I've had this problem before with my old interface. Back then, I changed the start baud rate, and it worked. But that was a long time ago, and I can't remember exactly what I changed.'

Here are the details regarding the 'hardware':

The diagnostic interface was built according to the following circuit diagram:

http://www.dieselschrauber....apter%20trimmbar.png

Car is a 2-bedroom, 4-person G40.

The PC has an 800 MHz AMD Athlon processor and 512 MB of RAM.

VAG COM Version 30.2.2 Full Version, German.

It would be great and helpful if someone could offer some advice.

Best regards,
Benjamin

PS: Any errors in the wiring can be completely ruled out. Everything was also measured and adjusted according to the instructions. Therefore, there must be an error in the VAG COM settings.

The search function should be your friend and helper! There are already countless posts on this topic.

Hello Joerg,

I have already searched for solutions, but I haven't found anything that specifically addresses this problem with Ulf's adapter.

Best regards, Benjamin.

Hi.

Regarding the adapter check:

http://www.dieselschrauber.de/TestOK-Adapter.zip

Good luck.

'So, my laptop occasionally throws error messages at me, especially when I close programs in unconventional ways. Then, the COM component freezes, and I have to shut the thing down.'
Under normal operating conditions, there are no problems.

Given the excellent design of the circuit board, it's reasonable to assume that an oscilloscope could be used to measure the signal levels.

Is the DIY D-SUB adapter okay? It looks like it could be a short circuit hazard.

I always switch VAG-COM to the default settings when something doesn't work. This is usually the case with older control units. Since I have the settings on my car set to the maximum (data rate rules), I can't communicate with older vehicles. Then I set it to the default values, and it works...

CU Gremlin.

Thanks for the replies. A colleague at work built the adapters for me. Really ingenious work. One is based on Jeff Noxon's circuit, and the other is based on Ulf's new circuit.

@Ulf: Where in Saarland are you from? I'm from Blieskastel!

Best regards,
Benjamin

PS: I'm going to run the adapter test using the software now!

Okay, so far everything is working positively with the test program, and the LED test in VAG-COM is also working, but the adapter is still NOT being recognized.

Best regards, Benjamin.

benjamin wrote:

So, with the test program, everything is working positively, and the LED test in VAG COM also works, but the adapter is still NOT being recognized.

Hi Benjamin,

If the "beam test" is successful (up to what baud rate?), the communication in both directions on the K-line is generally OK.

Have you tried optimizing the baud rate using the VR 2 and VR 3 trimmers?

I am from Kleinblittersdorf.

Hi Ulf,

As I mentioned before, I don't really know much about this. I had a colleague build the adapter according to your schematic. It looks great, and he said he had checked all the values and that it was working on his laptop. But it's not working for me. The baud rate test is also failing. The green LED is blinking, but I can't see any black bar :/ I'm starting to get desperate.

Best regards, Benjamin.

benjamin wrote:

. . . and he said he had also measured everything and that all the values were OK, and that the adapter was also working on his laptop. But it doesn't work for me. Also, the baud rate test is not working. The green LED is blinking, but there is no black bar :/ I'm desperate.

Hi Benjamin,

Do you have any proof, other than your colleague's statement, that the thing is running on his :laptop}?

Otherwise, I can only refer you again to the description of the adapter function control using "set K-Line," etc.

If the "static" measurements are okay, the beam test should also show some result or be optimizable via a trimmer.
Unless extremely slow optocouplers were installed, which wouldn't even be able to achieve the lowest baud rate of the adapter test...

Hi Ulf,

I can only rely on his statement. He built an interface for me before that ran on my old laptop. Unfortunately, I don't have that laptop anymore. And the old interface that ran on the laptop no longer works on my PC either.

Best regards, Benjamin.

benjamin wrote:

And the old interface that used to work with the Lapi is no longer working on my PC either.

Well, it seems a faulty COM port on the PC might be the issue... Can you switch to other ports?

I just tested my digital camera on COM ports 1 and 2, and it works on both. I also tested it on a colleague's computer, and it didn't work on either of the adapters. I'm really starting to get frustrated.

Best regards, Benjamin.

Hi.

So, step by step, following the accompanying text of the adapter test software , measure everything until the bug is found.

"As a supplement, it might also be helpful to refer to the description of the VAGCOM dialog."

Lots of patience and good luck...

Hi Benjamin, I've also encountered the problem where some computers don't recognize the adapter. It's probably due to the interface specification not being followed. Try using an adapter with an RS232 receiver.

Regards,
Maik.

Where can I get an adapter with a receiver like that?

Best regards, Benjamin.