CAN allows for data packets with a payload of up to 8 bytes, to send messages longer than 8 bytes it is necessary to use a transport protocol. The OBD-II specification for example makes use of ISO-TP (ISO 15765-2). Volkswagen however uses it's own transport protocol in its vehicles, known as VW TP 2.0.
This is a quick write-up of my understanding of the DTCs and switches in the Siemens PPD and SID803/SID803A/SID206 ECUs. I will be working with the PPD SN100L8000000 file from the sample BDM files.
DTC table entries
There is a table in each file which contains Diagnostic Trouble Codes (DTCs). If you view the table in hex you will see they match up with P-Codes i.e. codes for the powertrain.
PPD Maps is open source (GPLv3) software for detecting maps in Siemens ECU dumps. Supported ECUs are PPD, SID206 & SID803A. There is partial support for SID803 and barely working support for SID201
The software will identify the corresponding axes for each map and also give a list of DTC/P-codes. It will also find single byte switches to turn off DTCs
The file must be a full read of the ECU i.e. BDM. A partial read using a tool such as MPPS or similar will not work.
VAG Blocks is open source (GPLv3) beta software for reading VAG group specific measuring blocks from an OBD-II port using an inexpensive ELM327 type adapter. Both Bluetooth and USB adapters have been tested on Windows & Linux. Sample rates of up to 12 samples per second have been achieved.
Various control modules are supported such as the engine ECU and gearbox. Values such as boost, oil temperature, DPF soot loading and current gear can be plotted in program and logged to a CSV file.