Think of CAN as a shared conversation between controllers. A message can describe a measurement or operating state needed elsewhere in the vehicle. Diagnosing the conversation requires both electrical information and the correct vehicle context; seeing a pair of wires is not enough to identify every network type.
The physical link
Texas Instruments describes a typical high-speed CAN arrangement with a 120-ohm termination at each end. Two such resistors in parallel give approximately 60 ohms. This explains the familiar number; it does not make it a universal pass/fail test for every pair of diagnostic-socket pins or every vehicle network. TI termination example.
What one reading cannot tell you
A resistance result cannot show the timing of an intermittent dropout or identify the content of a missing message. It also cannot establish that a controller is awake and reporting valid data. The measurement point and the network’s actual arrangement matter. A gateway may separate the diagnostic connector from the network under investigation.
Resistance checks must follow the manufacturer’s specified power state and isolation procedure. Do not use a resistance range on a powered circuit. Avoid applying a generic CAN test to airbag wiring, high-voltage connectors or an unidentified communication pair.
What the workshop needs
Save the reporting module, complete DTC and the conditions in which it returns. Ask that any recorded waveform or measurement includes the location, operating state and test equipment settings. “CAN tested good” without that context is difficult to use when assessing a removed ECU.
A module can report missing information while its own electrical connection remains intact. The supplier of that information, a gateway or a supply issue may need investigation. Start with a full network scan and vehicle wiring information rather than a parts order.
Prepare a diagnostic enquiry or explore the network guide category.
Reviewed September 2026. Use the complete manufacturer-specific fault description and vehicle repair information.