VAG-COM Adapter Status: Not Found/Ready

Hello,
'I soldered the adapter together today. It worked better than expected on a perforated board. Since I don't yet know how to obtain a proper OBD II connector, I'll have to settle for some 'practice runs' for now. The LED test is running successfully (LEDs 1 and 2 blink simultaneously and alternately). During the interface test, without a vehicle connected, the following message appears:'
VAG-COM adapter status 3: Not found or not ready.
Is this normal, or should I look for another error?

I simulated the vehicle's operating voltage for the adapter (12V connected to R19).

Hi Andy,

With a correctly functioning adapter that is properly powered by the vehicle, the message should read "Adapter found and ready" – provided that you have specified the correct COM port in VAGCOM.

During the LED test, LED 3 should also blink intermittently – I suspect there's still a bug somewhere.

Hello Ulf,

I actually had a mistake in the circuit with LED 3. The LED test in VAG-COM now looks like this:
4 x Blinking LED 1+2.
10 x LED running lights, sequence: 1 > 3 > 2.
4 x Blinking LED 1+2.
Then comes the LED test, which passes (no error checking is performed on the PC side).
It still remains at:
VAG-COM adapter status 3: Not found or not ready.
I think it's very important to write an operating manual, as many replicas fail at this stage.
Could you please recreate the test setup at your end so that you can determine the exact VAG-COM error messages?

AndyO wrote:

I think it's very important to write a commissioning manual, as many replicas fail at this stage. Can you recreate the test setup at your location to reproduce the exact VAG-COM error messages?

Hi Andi,

I actually included a DIY hardware test, which is described in the technical article --> It's a functional test using 12 volts and a few jumper wires, but without a PC.

Have you ever tried that before?

The LED test on the PC (with a working adapter) looks very confusingly blinking to me.
Therefore, I don't think it's a great idea to include that in a description that could be misunderstood by other people in at least 5 different ways...

First of all, thank you for the commissioning instructions. I unfortunately didn't see them before. I've also made some progress. The T3 transistor isn't amplifying enough. This is due to the tolerance of the DC current gain factor of the BC547 transistor (β = 75..900). With a voltage divider of 150 kΩ (R12 / (R13 + VR2)), the maximum base current is 6V / 150 kΩ = 40 μA. The load circuit, including OK3, needs approximately 20 mA to fully activate. This means the current gain needs to be at least 200. Unfortunately, my T3 doesn't achieve that. I'm going to try it with a Darlington transistor, the BC879. I'll report back around 4 PM.

Hello Andy0,

It's possible that the adapter is correctly assembled, but Vagcom displays "Adapter not found..." and it still works. I observed this with Vagcom versions >= 0.81. With version 0.78b, Vagcom reported that the adapter was found.

I have no idea why that is. However, the newer versions of the OBD2 interfaces that are included with VAGCOM no longer have optocouplers. Perhaps that is the reason why the detection routine has been changed compared to the older VAGCOM versions.


Best regards, Georg.

After replacing the T3 transistor with a BC879 Darlington transistor and adjusting the voltage divider resistor R13 from 22kΩ to 150kΩ, the adapter behaves as described in the test scenario. Previously, it was not possible to properly activate T3. The LED sequence now proceeds as follows:
1 is greater than 1 + 2.
4 * (1 on, 2 on, 3 off) > (1 on, 2 off, 3 on)
9 * (1 on, 2 off) > 3 on > (2 on, 1 off) > 3 on
5 * ((1+2 on, 3 off) > 4 * (1+2 off, 3 on))
1 * short, green.
The error message remains the same. I would be very grateful if someone could confirm this sequence. I think it would be interesting for everyone to know how the sequence runs without the control unit. I learned from the VAG-COM forum that the adapter cannot be tested without a connected control unit. I asked Ulf to check the power amplification of the T3. Furthermore, the resistors R5 and R6 are named twice in the circuit diagram.

Hi Andy,

Your calculations are not quite correct.

AndyO wrote:

With a voltage divider R12/(R13+VR2) of 150 kOhms, a maximum base current results in 6V/150 kOhms = 40 μA.

The voltage at node R12/D7 can be no more than approximately 1.2 volts; any voltage above that will cause D7 and the base-emitter junction of T3 to conduct, grounding the signal.
At R12, a nominal voltage drop of (12 - 1.2) = 10.8 volts occurs, resulting in a current of 72 µA.
R13 and VR2 consume: 1.2 V / 122 kOhm = approximately 1 µA, so T3 receives a maximum of around 70 µA.

Quote:

The load circuit with OK3 requires approximately 20mA to pass through.

The photodiode requires approximately 1 volt, so there is a nominal voltage drop of about 11 volts across resistor R5.
11 V / 1 kOhm = 11 mA, representing the maximum collector current for component T3.
11 mA / 70 µA results in a required current gain of approximately 160.

When I perform hFE measurements on BC 547 transistors using a multimeter, I consistently get results greater than 300.

Regardless, when there's a voltage applied from the auto side without activating the K-line or OK2, the collector voltage of transistor T3 should be below approximately 1 volt. As long as a standard BC 547 can handle that, I don't think a Darlington transistor is necessary.

AndyO wrote:

I learned from the VAG-COM forum that the adapter cannot be tested without a connected control unit. I asked Ulf to check the power amplification of the T3. Furthermore, in the circuit diagram, the resistors R5 and R6 are named twice.

Hi Andy,

Okay, mine is detected as "found + ready" as soon as I apply voltage from the car side, even with the K and L lines disconnected.

(@Georg: For me, the German version (81a) and the English version (81b) are both working with my optocoupler adapter 2.2.)


To increase the power output of the T3 amplifier --> see previous post.

The double naming of R5 and R6 is, of course, terrible .
I will make the changes and email Rainer a new version.

Hello Ulf,

'At the very least, include a note about the current amplification in the schematic. Anyone who doesn't know that is on their own. It would be better to try it with a Darlington BC879. Unfortunately, I'm still missing the connector.'
P.S. The current VAG-COM version is 2.082d. Will that work?

AndyO wrote:

Include at least a note about the current gain in the schematic. Anyone who doesn't know this is on their own. It would be better if you tried it with the Darlington BC879.

Hi Andy,

I would be somewhat skeptical about the achievable data transfer rates when using a Darlington as a T3.
"The circuit isn't straightforward: with R10 = 4.7 kOhms and R11 = 10 kOhms, I couldn't get it to work properly in a real-world application."

Is a Darlington transistor guaranteed to be no "slower" than a 547 when used as a T3 in this circuit?
I lack the specialized knowledge regarding the various transistor parameters.

What would also be interesting to me is: have you ever measured the collector voltage at pin T3 = BC 547 when the signal is at a high level on the K-line?

Our responses overlapped (do you have Netmeeting?). The cutoff frequencies of these small transistors are in the two- to three-digit MHz range. You can build an FM oscillator using a BC547.
Since we're operating in the kHz range, that's not a problem. I just didn't expect the operating point to be so critical.

AndyO wrote:

I just didn't expect that the working point would be critical.

Hi Andy,

That surprises me too, especially since this is the first case of its kind that I've heard of.

I will include some relevant notes in the offline exam instructions and ask Rainer to modify the text accordingly.