Thread: KWP2000 startDiagnosticSession help!

Originally Posted by fanl

Hi guys!

I am having a hard time to understand what is the DiagnosticSession services of the KWP2000 fiat specification (http://storage.fiat-bg.org/Diagnosti...at_kwp2000.pdf).

When I issue startDiagnosticSession I must provide two bytes, one for the type of diagnostic and other for the baud rate. (page 20 and 21 in the pdf document of the above link)

Hex 81 means I will start a DiagnosticSession OBDII Standard, but, where is this communication going to happen? In the K line? Other line? How can I test if the session is working.

My primary objective is to get any info from sensors (speedo, temp, etc..).

Thanks for any help.

Can you describe your setup (hardware, software)?

Originally Posted by fanl

I made myself the whole setup. I am using only k-line to communicate, it is a ARM7 microprocessor the brain of the system. The software is being writen by me. I can do any change on software and hardware.
Be more specific in order to me understand what you need to know.
Thanks!

Be prepared to have lots of patience, if you want to get this to work. :-)

First of all, you need to do either 5 baud or fast init. You have not indicated whether you're already doing this.

Second, you need to send the StartCommunication Request (page 11 of your document). The format is:

<format byte><target address><source address><service id><checksum>

You always communicate on the K line (except during initialization).

Vitaliy

By the way, have you noticed this?

C O N F I D E N T I A L
THIS DOCUMENT MUST NOT BE REPRODUCED OR CIRCULATED TO THE THIRD PARTIES
WITHOUT PRIOR WRITTEN CONSENT BY FIAT AUTO S.P.A. IN CASE OF DISPUTE
THE ONLY VALID REFERENCE IS THE ORIGINAL ITALIAN EDITION

Originally Posted by fanl

Lol! They are the ones who did spread the document on internet, they even hold a server with these files! lol!

I did the init, I did send the StartCommmunicationService and got the right awnser, then when I issue the startDiagnosticSession I got a positive awnser too, the, I've got no IDEA what do I do with the Session! heheh!
I mean, I request a Session providing the 83h, witch means that the session will be OBDII standard, but but but, I don't what to do with the session.
OBD-II standard says that the sensors values are in the $01 service, but even after the Session has been started I couldn't get good awnser from the $01. I really do not want to have to read memory blocks and interpret it, as it is commonly done in Fiat cars.

So, what are your recomendations o'great Vitaliy?
(hehe)

Thanks.
FanL.

That's right you mortal, bow to your master! (hey, you started it... )

So can you copy/paste what you get so far? If the vehicle is not EOBD compliant and responds with 7F to mode 1 requests, then you don't have many options.

Best regards,

Vitaliy