Passat 3BG: No Connection? Troubleshooting Guide

Good evening.

I am unable to establish a connection to the control units in the Passat.
'When I try to connect, for example, to the engine control unit, it displays the following error messages: 'Adapter Status 2', 'Incorrect COM port setting', 'Adapter not connected', 'Short circuit on the K-line'.'
When switches K1 and K2 are in position, it attempts to connect, but it stops working after a few tries.

When I test the adapter in the options, it says 'Adapter not found' for K1/L.
and for K1/K2: adapter found, IC level shifter or something similar.

The Passat was manufactured in January 2003, has a 130 horsepower TDI engine, an automatic transmission, and climate control.

I just tested the adapter again on my Passat 35i TDI, and everything works fine. It also works without any problems on a Golf 4 TDI from March 2003.
The VAG version is 402, and the adapter is the KKL RS232 adapter available here in the shop.

I hope you can make something of this and help me .

panther

Hi Panther,

Please go to the download section (customer account) of the shop; currently, VAG-COM 409.1 is available for your hardware.
Regarding your problem: as I see it, the K-line is likely being blocked somehow. Try disconnecting the car's battery for 1 minute (don't forget the radio code) and check if the K-line is accidentally shorted to ground or +12V (e.g., due to improper radio installation).

Best regards, Rainer.

How can I tell if the K Line has a short circuit? There's an original VW radio installed in the car.
Will disconnecting the battery for a minute also clear the error memory?
That's something I'd prefer to avoid, if possible.


panther

Hi,

"Errors are typically stored in the EEPROM, which retains data even when power is lost. I have no idea which control units might be exceptions to this and store errors in RAM instead."
Let me see...
- the voltage at pin 7 in the diagnostic connector relative to ground.
- The short-circuit current from pin 7 to ground should be limited; a 100-ohm resistor would be beneficial to prevent any components in the wiring from burning out in the event of a fault.

Is the diagnostic connector properly seated in the socket? The socket can be larger or smaller depending on the model, and the connector can sometimes be a bit difficult to insert.

Best regards, Rainer.