What this test proves

Check termination and wiring on a confirmed two-terminator high-speed CAN segment. This does not verify communication quality.

Tools

  • Digital multimeter
  • Vehicle network topology and shutdown procedure

Preparation and precautions

  • Power down the segment and follow the prescribed isolation/wait procedure. Verify no voltage before selecting resistance.
  • Do not assume the diagnostic connector exposes the network being diagnosed. Gateways, switched termination and other bus types change the test.

Connections

  • Measure between the identified CAN High and CAN Low conductors at the specified accessible point on the isolated segment.

Equipment settings

  • Resistance mode only after confirming the circuit is de-energized.

Test sequence

  1. Identify topology and expected termination.
  2. Measure the complete segment.
  3. If abnormal, follow the diagram and OEM isolation sequence to test branches and terminators.
  4. Reconnect everything and verify communication after repair.

Expected signal / readings

Two 120-ohm end terminators in parallel give approximately 60 ohms, but only when that topology is actually present.

Interpreting results

  • Approximately 120 ohms can indicate only one visible terminator; topology and gateway isolation must be considered.
  • Very low resistance may indicate a short or extra termination. A normal reading does not rule out intermittent faults or poor signal quality.

Common mistakes

  • Measuring a live network
  • Applying 60 ohms to LIN, fault-tolerant CAN or every gateway branch
  • Unplugging nodes without understanding termination