A long diagnostic reply can be split across several CAN frames. Seeing its first frame does not prove that the complete response reached the diagnostic application.

What to check next

Keep a raw capture covering the request and the full waiting period. Check whether the receiver supplied the expected flow control and whether later frames appeared. This helps separate an incomplete exchange from an ECU that never answered at all.

Useful information for an enquiry

Send both transmit and receive traffic with timestamps and the diagnostic operation.

A partial response should not be decoded as though it were complete. Missing bytes can change the meaning of the apparent result.

Speak to AXION

For CAN-bus and vehicle-network diagnostics, send your vehicle details and fault report. Workshop assessment is in Didcot, Oxfordshire. Suitable postal or remote work is confirmed before booking.

Technical background from python-can-isotp. The referenced design explains the principle; the vehicle-specific procedure determines the repair.

Related reading — ISO-TP flow-control timeouts during a module data read. Browse all vehicle-electronics diagnostic notes or return to the repair library.