On a conventional network with two 120-ohm terminations, adding a third changes the total load. More termination is not automatically better.

Interpreting the evidence

If communication changed after fitting an accessory, breakout box or replacement assembly, identify everything connected to the pair before interpreting resistance. Use the vehicle shutdown and disconnection procedure. Compare the actual circuit arrangement with the wiring information rather than assuming every diagnostic socket exposes the same bus.

Keep this evidence

Record which equipment was attached and whether its termination setting was enabled.

A resistance reading describes that test configuration. It does not establish that an ECU is defective, and resistance checks must not be made on an energised circuit.

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 Texas Instruments. The referenced design explains the principle; the vehicle-specific procedure determines the repair.