Automotive — VAG
Select Automotive → VAG. The VAG package uses the shared Automotive tools package; the package manager offers to install the required dependency.
Traffic source
Connect a CAN adapter and set the bus bitrate in connection settings. Alternatively, load a .ptrc file or a supported CAN Hacker .trc file in Tracer. Diagnostic decoding requires traffic between an external diagnostic tester and an ECU.
Tracer layers
| Layer | Contents | Purpose |
|---|---|---|
Physical | Source CAN frames | Inspect frame identifiers and bytes |
Transport | ISO-TP and TP2.0 | Inspect message assembly and transfer control |
Protocol | UDS and KWP2000 | Find a service, request, positive or negative response |
During normal reception, a CAN adapter delivers individual frames, while a diagnostic message may span several frames. The Transport layer shows message assembly and transfer control; the Protocol layer shows the service, parameters and response type. Select the Protocol layer to inspect a complete diagnostic response, and the lower layers to check its transmission.
For TP2.0, start capture before channel setup: application decoding may be incomplete without that context. Each layer has its own filter and field catalog. The application layer also has a separate TesterPresent visibility control.
Monitor shows recurring CAN frames, their latest bytes, period and count. Use Tracer to analyze diagnostics at message level.
This guide covers observation of diagnostics over CAN. A recognized diagnostic service in a trace does not mean that the beta version provides a tool for executing it.
During an active hardware ISO-TP operation, Tracer receives complete messages and raw CAN frames are unavailable. Monitor does not represent all traffic during this period; .ptrc and .log exports do not include hardware messages. See traffic statistics for the corresponding metric limits.
Services and ECU responses
On the Protocol layer, select UDS or KWP2000 according to the traffic actually present. Then narrow by addressing, service and, when included in the message, DID, RID or local identifier. A trace may contain several ECUs; match messages using addressing and timing.
The service field groups a request with recognized responses for the same service, while rawSid contains the message's actual SID. A negative response does not contain the original request's DID/RID: filtering by identifier does not automatically include it. To investigate a rejection, return to a service filter and inspect the surrounding traffic.
NRC 0x78 (ResponsePending) means processing has not finished yet. To see how the operation ends, inspect subsequent responses in the same exchange, not just messages with this NRC. To investigate TesterPresent, enable it with the separate visibility toggle.
Diagnostic message transport
On the Transport layer, inspect ISO-TP flow control or TP2.0 channel setup, acknowledgements and closure. Interpret waiting, overflow and receiver-not-ready states alongside adjacent messages. An empty selection means no decoded messages matched; it does not prove that communication is healthy.
To compare with source bytes, switch to the Physical layer and use CAN IDs from your trace. UDS/KWP2000 fields are unavailable on this layer. Field values and applicability are listed in the VAG reference.
When saving results, note the layer, filter expression and capture boundaries. If the trace starts partway through an exchange, mention that in the description.