CAN Bus Access Denied: Troubleshooting Guide

During various test drives, I have already had two vehicles that did not allow access to the control units.
Once a Golf VI, and once a V'er.

What could be the reason for that?
(Made several attempts. Used: VCDS)

Were any aftermarket radios installed? These often cause a short circuit on the CAN bus (K-line) if not properly wired according to the manufacturer's instructions, which can then disable various functions.

Alternatively, you can run a final test under the settings menu, which will also detect and display various errors.

Is a CAN cable available?

The adapter cable is working fine (so far, at least).
And I didn't notice anything special about the radios. They were just the ones that came installed from the factory. Of course, I can't look behind them.

Hi Aunt Martin!

What Klaui was trying to say: Do you also have the OBD2 cable with both KKL AND (!!!) CAN?
See: http://shop.dieselschrauber.de/vcds-obd2-profi-diagnose-kkl-can-p-46.php

Otherwise, in such a case, I would always try to perform a full system scan.
It's highly unlikely that you wouldn't be able to find any diagnostic trouble codes (DTCs) with working hardware, unless the OBD port has been disabled (e.g., for theft prevention).

Best regards from Munich!

Is this a cable for CAN?
Exactly here, it was purchased.
And I've also been successfully connected on several occasions.

I had tried everything to get even the smallest piece of a control unit, but nothing worked.
I had the same problem with my old VW Golf back then. There was nothing I could do about it.

Next step or question:
The LED on the VCDS cable must change from orange to GREEN when it is connected.
If the light doesn't illuminate at all or is red, it could be due to the car itself or a faulty/damaged OBD port.
(which brings us back to GTI-TDI's suggestion!)

Best regards from Munich!

Yesterday, I didn't see the LED light up. However, during testing, the program indicated that the connection was working correctly.

The LED light on the first car was green.
(with the same result)

I don't think it was a hardware issue. Because it works on other cars.

Hi Aunt Martin!

Then the only thing that will help is this:
When you encounter the next error, please take a Screenshot of the pop-up "test window" and note what the LED was doing.

Best regards from Munich!

Okay.

I will try to remember that .

Hello Martin,

You purchased in 2007: A semi-professional EOBD/OBD2 diagnostic system, KKL (USB).

So, no CAN functionality, which means that cars that use CAN for diagnostics won't work either.
An upgrade to https://shop.dieselschrauber.de/vcds-obd2-profi-diagnose-kkl-can-p-46.php.
It is possible. If you are interested, please contact me directly.

PS: Here, you can see which VCDS diagnostic system is suitable for which VAG vehicles.
Either cross-manufacturer, purely for OBD2.

Best regards, Rainer.

Data abuse here...

No. Your database is incorrect.
It was a CAN cable. You initially sent me the wrong cable.
certainly.
It was then corrected.

Quote:

Golf VI, and a V'er.

Both use CAN, but you're saying it doesn't work... Please send me a private message with the serial number and model designation on the label of your diagnostic cable.

Best regards, Rainer.

OK.
Then it's probably the cable after all.