A CAN frame may include padding around a shorter diagnostic payload. Treating those bytes as actual returned data can create a false parameter value or fault description.

What to check next

Use the transport length and the correct decoder to separate payload from padding. Preserve the raw frame alongside the decoded result when investigating a discrepancy between tools. Check the supported padding configuration if one tool rejects an exchange another accepts.

Useful information for an enquiry

Include the complete frame and the decoder settings.

Do not remove bytes by appearance alone. Length and addressing information determine which bytes belong to the message.

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 the project maintainers. The referenced design explains the principle; the vehicle-specific procedure determines the repair.

Related reading — ISO-TP addressing mode can shift where the payload begins. Browse all vehicle-electronics diagnostic notes or return to the repair library.