When I did my display for my old mk6 Jetta TDI, I just requested it the same way VCDS does it. You get exactly what you want, when you want it.
Besides that, you can't find soot load just floating around on the power train bus (not that I know of anyway), so I had to get that from the correct measuring block.

That's how I ended up doing it in the end, one request for each item... It does slow down refresh a bit, but still real time enough for me.

In the VW TP2.0 protocol, there is a facility for assembling multiple request to batch it in one transaction, but I never had a chance to get it to work.

So, did you manage to successfully request anything? If so, do you know what messages do what? (even better, is there a document here on this site detailing it at all?)

I am currently doing similar, but by sniffing the bus directly.

Perfect thanks.

I located all the parameters I was after, there is still 1 which I cannot find. That is real time AFR (or, raw actual lambda value). Not user requested target lambda.

I am guessing, that it is not actually sent out over the CAN bus?? And that the only way to grab it is to request is? Could anyone clarify this?

Hi

I know this is one of my first few posts but i have been doing this on and off for many years. my personal view is to connect direct to the engine CANbus (instead of going thru gateway) and just listen to the values on the bus, as most of the values you are looking will probably be transmitted.

in my view this reduces bus load on the canbus,gateway and ecu as it does not have to process what values you want before it can transmit. you should find reading directly off the bus will also give you a faster refresh rate.

Hope that helps

First tip is ignore almost all the posts in this thread. Besides nubcake and seishuku it doesn't seem like anyone knows what they are on about.

You have two options.
You either connect to the CAN bus and passively sniff the data messages.
Look at ME7 FR in the "CAN" module, it contains all the messages the ECU sends including scaling and structure.

Or if you want some sort of data that is not in those messages, then you will have to set up a diagnostic session to the ECU like a scan tool does.
The Touareg has KWP2000 over K-Line. Nothing special there, simply fast init and then get the spec and just ask for things the same way you would do with VCDS.

You are going to have to compile a list of measuring groups and then a measuring block to data item mapping.
In KWP2000 you don't need to worry about scaling because each measuring block consists of 3 bytes - ID, A and B.
You can find most of the important formulas here to calculate the end result:
https://www.blafusel.de/obd/obd2_kw1281.html

I would advise against using DDLI or ReadMemoryByAddress because this is ECU specific. KWP2000 with fast baud and low comm timings is very fast anyway, you should not have refresh rate issues if you don't request more than 4-5 measuring groups, which is plenty.
You can improve the response by only requesting data that is currently on-screen for example.

their is already a free app that works with a bluetooth dongle , https://github.com/theksmith/CarBusInterface/wiki