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Author Topic: Read VAG DTCs with KWP2000?  (Read 5637 times)
trichard3000
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« on: July 14, 2015, 03:07:12 PM »

Anyone know the protocol spec for the VAG version of 14230-3?

I'm noodling on my old, python-based, KWP2000 implementation and I'm trying to figure out how VAG implements the "ReadDiagnosticTroubleCodesByStatus" service from ISO 14230-3. 

The service ID is 0x18.  In the Swedish version, it looks like this service should take 0x18, 0x02, 0xFF, 0xFF and return all DTCs with status.  0x02 is "RequestStoredDTCAndStatus" and FFFF is the group ID for all DTCs. 

I'm getting a response code of 0x12 (subFunctionNotSupported-invalidFormat) which suggests that I'm feeding the service the wrong parameters.  If I look at the generic 14230-3 spec, the grouping function (groupOfDTC) is individual to manufacturer. 

Thanks for any info you can share!
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trichard3000
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« Reply #1 on: July 14, 2015, 03:26:28 PM »

Whoops, I may have just answered my own question.  

I dug back in to the Fiat spec for KWP2000 here in the forum and they use 0x18 0x00 0xff 0x00 for the service.  That's now returning data successfully.  

I haven't parsed through the data to see if the data actually makes sense yet, but I think I'm on the right track.  If you have any info about this, please share, thanks.

Update:  Yep, this sequence returns the number of stored codes and then a list of three bytes where the first two represent the "P" code and the third is a bitmap showing the code status.  Good stuff!

I'm running on an M-box btw. 
« Last Edit: July 14, 2015, 08:14:30 PM by trichard3000 » Logged
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