VAGCOM: Dashboard Warning Lights Explained

Hello.

The well-known "ticking" sound in the VAGCOM interface causes the slew rate of the rising edges to be switched (approximately 1 or 2 volts per microsecond with a 2.2 kOhm pull-up resistor) - I observed this with an oscilloscope connected to the K-line.

But why all of this?
Can anyone make sense of that?

Hi Ulf,

The "Tickern" is a relay located in the instrument cluster. Its purpose is to switch the K-line connection from the immobilizer/instrument cluster to the engine control unit (ECU). That's all it does! Normally, all control units (ECUs) in the car are directly connected to the K-line, but the ECU is accessed via the instrument cluster. This makes sense, as the immobilizer needs to communicate through the instrument cluster.
I need to take another look at the wiring diagram of the combination unit to figure out why the signal changes when the relay is activated.

Bertil wrote:

The ticking is a relay in the combination instrument.

Hi Bertil.

Are you sure (for all vehicles) ?

My station wagon, in any case, is not capable of being diagnosed, so why would it have a K-connector ?

In the wiring diagram, the K connector doesn't seem to connect to the combination instrument panel.

Hello Ulf,

You have an immobilizer system, and the control unit for the immobilizer is ticking. This is something that can be diagnosed. Listen carefully; the unit is located directly behind (under) the instrument cluster.
I also have this configuration in the bus, and I know that because I tested the components while they were being installed.

Hello.
Wolfgang.

Wolfgang, syncro16 wrote:

You have an AFN engine with an immobilizer, so the immobilizer control unit is active and can be diagnosed.

Hi Wolfgang,

Depending on the context, that could be a good thing.

The "funny" thing is that the relay doesn't always click .

Sometimes, in the dialogue, there is complete silence, and at other times (with the same control unit!), it ticks again...
The conversation is always completely normal...

Hi Ulf,

I've forgotten my G3 story again . You are correct that in your vehicle, the WFS is a separate ECU, but in newer vehicles, the WFS is integrated into the combination instrument. In any case, the K-line for the engine ECU is passed through the WFS ECU.

Quote:

The "funny" thing is that the relay doesn't always click

.

I'm still not clear on when that feature activates. I can understand it during the initial dialog setup, but otherwise, I can't make sense of it.

Hello,
Today, I tried to check my car (Passat TDI, 1997, AFN engine, type 3B) using the interface posted on the dieselschrauber-site by Ulf, and the free version of VAG-COM.
'In addition to the clicking sound behind the instrument panel, there was also erratic flickering in the indicator lights (speedometer, tachometer, fuel gauge, coolant temperature) and the daily mileage display and digital clock reset to zero. While driving, the instruments continued to fluctuate wildly. Now, when the ignition is turned on or while driving, the daily mileage display only shows 'FAIL.' Disconnecting the battery for about 3 minutes temporarily resolved the instrument behavior. However, the daily mileage display still shows 'FAIL' when the ignition is on. Also, it is no longer possible to adjust the service intervals using the adjustment knobs on the speedometer and clock.'
Has anyone got any ideas on how to get rid of this annoying 'FAIL' message? By the way, there was never any entry in the error memory. The VAG workshop read the memory, and while my interface is recognized by the VAG-COM software, it doesn't seem to work otherwise.
Thank you for your help in advance.
Regards,
Max.

Hello,
This morning, when I started driving, the daily mileage display was working again. Also, the service interval setting is working correctly. There are no more 'FAIL' messages anywhere.
Let's see what happens.
Regards,
Max.
PS: For those who catch on quickly,
You learn something new every hour when you're building adapters!