CAN Bus Termination Resistance: How to Test 60 Ohms and Interpret the Result

CAN bus termination resistance is one of the fastest electrical checks for a high-speed vehicle network. On a conventional high-speed CAN circuit with two 120-ohm terminating resistors, a multimeter connected between CAN High and CAN Low should read about 60 ohms because the two resistors are connected in parallel.

That reading is useful, but it is not a complete network diagnosis. Architecture and measurement location affect what the meter sees. Always use the wiring diagram and manufacturer procedure for the exact vehicle.

Why a Healthy High-Speed CAN Bus Reads 60 Ohms

A typical high-speed CAN backbone has a 120-ohm termination at each physical end. The termination matches the approximate characteristic impedance of the twisted pair and reduces signal reflections as voltage edges travel along the bus. The two resistors appear in parallel when measured across CAN High and CAN Low.

For two equal resistors in parallel, total resistance is half the value of either resistor: 120 divided by 2 equals 60 ohms. Texas Instruments describes standard termination as one 120-ohm resistor at each end, while Subaru training information archived by NHTSA uses the same calculation for a vehicle network measured at the data link connector.

Some modules use split termination, commonly two resistors with a capacitor at their midpoint. The effective resistance across the pair can still be approximately 120 ohms at each end and approximately 60 ohms for the complete bus.

Confirm That the 60-Ohm Test Applies

The familiar 60-ohm expectation applies to many high-speed CAN and CAN FD backbones, not every communication circuit in a vehicle. Low-speed fault-tolerant CAN, single-wire CAN, LIN, FlexRay, Ethernet, and manufacturer-specific networks can use different topologies and values. A gateway may also separate several CAN networks, so the diagnostic connector may expose only one segment or provide access through the gateway.

Identify the affected modules in a topology diagram before testing. Confirm the network name, connector pins, terminating modules, splice locations, and whether the gateway remains electrically connected with the vehicle powered down. For comparison, our LIN bus diagnostic guide explains why LIN circuits cannot be judged with a CAN termination test.

How to Measure CAN Bus Termination Resistance

Save the full vehicle scan and note which modules communicate, which are missing, and all current or history U-codes.
Switch the ignition off, remove the diagnostic interface, and follow OEM shutdown and battery-disconnection instructions. Preserve settings or high-voltage safety steps where applicable.
Allow modules, retained-accessory circuits, and network gateways to enter sleep. Never measure resistance on an energized circuit.
Set a known-good digital multimeter to ohms and verify the leads by touching them together.
At a standard DLC, high-speed CAN commonly uses pin 6 for CAN High and pin 14 for CAN Low. Confirm these pins on the vehicle diagram before probing.
Measure directly between CAN High and CAN Low without spreading terminals or shorting adjacent pins.
Record the stable value and compare it with the OEM specification and network layout.

Resistance checks require no current flowing through the network. An energized module can produce a false or changing value and may expose the meter to voltage while it is in ohms mode. Infiniti service guidance, for example, specifies ignition off and battery disconnected for CAN resistance checks.

If the DLC is not electrically connected to the suspect segment during shutdown, measure at an accessible module or splice specified by the service procedure. Our guide to using a multimeter with diagnostic software covers lead checks, safe back-probing, and why circuit conditions must be controlled.

How to Interpret Common Resistance Readings

Approximately 60 Ohms

A stable reading near 60 ohms usually means the meter can see both 120-ohm termination paths. It supports continuity through the backbone between those terminators. It does not prove that every branch is connected, every module has power and ground, or signal quality is acceptable while the network is active.

An open branch to a non-terminating module can leave the backbone at 60 ohms while that module remains offline. Corrosion, excessive branch length, intermittent contact, or a transceiver fault may also cause communication errors without changing static termination resistance.

Approximately 120 Ohms

A reading near 120 ohms commonly means only one termination path is visible. One terminating module may be unplugged, unpowered in an architecture that switches termination, or separated by an open circuit in the backbone. The measurement can also be correct when taken at a disconnected terminating module itself. Use the diagram to decide which path is missing before disconnecting more components.

Approximately 40 Ohms

Three 120-ohm resistors in parallel equal about 40 ohms. This can indicate an unintended extra terminator, an incorrectly configured aftermarket device, or test equipment with termination enabled. Some networks intentionally use other arrangements, so verify the design before removing anything.

Near 0 Ohms

A very low reading suggests CAN High and CAN Low are shorted together, a module or harness has created a low-resistance path, or an inappropriate terminator is installed. Separate the network only at approved connectors and retest each section to narrow the fault.

Open Circuit or Very High Resistance

An OL display or very high value means the meter cannot see a complete resistance path. Possible causes include testing the wrong pins, both terminators being disconnected, a major backbone open, a disconnected gateway, or poor probe contact. Confirm the meter setup before condemning wiring.

Unstable or Drifting Resistance

A changing reading can occur while modules are still awake, capacitors are charging, or a gateway is switching state. Recheck the shutdown procedure and wait the specified sleep time. If the value changes when the harness is moved, inspect connectors, splices, and twisted-pair sections for intermittent contact.

What a 60-Ohm Reading Cannot Tell You

Static resistance does not show dominant and recessive voltage levels, edge shape, ringing, noise, arbitration errors, or intermittent dropouts. After confirming termination, reconnect power and use scan data to identify missing modules and error patterns. Check power, ground, and wake-up circuits at any suspect module before replacement.

Measure CAN High and CAN Low voltage only according to the OEM procedure. For difficult faults, use an oscilloscope at the correct test point and time base to compare both lines and inspect signal integrity. A network may measure 60 ohms when stationary yet fail under vibration, temperature, or electrical load.

A Practical Network Diagnostic Sequence

Preserve the scan report and map communicating versus missing modules.
Use the topology diagram to identify the shared network segment and its terminators.
Verify battery condition, module powers, grounds, fuses, and wake-up inputs.
Perform the powered-down resistance test under manufacturer conditions.
If abnormal, isolate approved sections and watch how resistance changes.
If resistance is correct, continue with voltage, waveform, and loaded-circuit tests.
Reconnect everything, clear only appropriate codes, and confirm all modules communicate.

This sequence prevents a common mistake: replacing a module because it is absent from the scan when the real fault is power, ground, wiring, or another node pulling down the bus. The broader network communication code workflow shows how to combine topology, scan results, and circuit tests.