The 60 ohm test: checking CAN bus termination with a multimeter

When several modules stop answering at once, the instinct is to start reading codes from whichever ones still respond. There is a faster first step, and it needs only a multimeter.

Background: CAN bus fundamentals for car owners.

Why 60 ohms

A CAN bus is a twisted pair — CAN-High and CAN-Low — terminated at each end with a 120 Ω resistor. Those resistors prevent signal reflections that would corrupt messages.

Two 120 Ω resistors in parallel measure 60 Ω.

So measuring across the pair with the vehicle off tells you whether both terminations are present and the wiring between them is intact.

Doing the measurement

1. Switch off the ignition and remove the key. Wait a few minutes for modules to sleep.
2. Set a multimeter to resistance.
3. Measure between pin 6 (CAN-High) and pin 14 (CAN-Low) on the OBD-II connector.

Reading	Meaning
~60 Ω	Both terminations present, wiring intact
~120 Ω	One termination missing — a module disconnected or failed
Near 0 Ω	Short between CAN-High and CAN-Low
Very high or open	Break in the bus, or the pins are not the ones in use
~40 Ω	An extra termination — often an aftermarket device

That last row is worth knowing. Some aftermarket installations add their own termination resistor, which lowers the total and degrades signal quality on a bus that was correctly terminated already.

Aftermarket accessories electrical faults and alarm and tracker installation.

What it does not prove

Honest limits, because a passing measurement can mislead.

60 Ω does not mean the network is healthy. It means the terminations and the wiring between them are physically intact. A module can still be transmitting corrupted messages, or the bus can be failing only when hot or when the harness flexes.

Not every vehicle uses pins 6 and 14 for the bus your tool needs. Some have several buses, and only one is exposed at the diagnostic connector. A high reading may mean you measured the wrong pair.

Some modules contain the termination. Removing that module for testing changes the reading legitimately, which can be confusing mid-diagnosis.

When to use it

Multiple modules unreachable. The most valuable case: U0073 control module bus off.

A scan tool that cannot connect at all, where the vehicle otherwise runs.

After an accident, where harnesses may have been damaged: after a minor accident, what to check.

After an installation. Anything wired into the bus recently is a suspect.

After water ingress. Water bridging CAN-High and CAN-Low in a connector produces the low-resistance case: damp carpet and electrical faults.

Voltage as a second check

With the ignition on and the bus active:

Line	Expected, at rest
CAN-High	Around 2.5 V, rising when transmitting
CAN-Low	Around 2.5 V, falling when transmitting

Both sitting at 0 V means no bus activity — a supply, ground or wiring fault.

Either sitting at battery voltage means a short to power, which will have taken the whole network down.

Before any of this: check the supply

The most common cause of a network that has fallen over is not the network.

A weak battery or a corroded ground makes modules reset and transmit garbage, which drives error counters up and takes controllers off the bus.

Check system voltage and terminals first: P0560 to P0563 system voltage faults and battery terminals corrosion.

The 60 Ω test is the second step, not the first.

Where to start

1. Check battery voltage and terminals.
2. Measure 60 Ω across pins 6 and 14 with everything off.
3. Check bus voltages with the ignition on.
4. Ask what changed recently — installation, accident, water.
5. Record all codes across every module you can reach.
6. Clear and re-scan to see what genuinely returns.

You can check this yourself. Pair an ELM327 adapter, open the free tier of the app and check connector voltage before assuming a network fault. Between that reading and a multimeter across two pins, most network mysteries resolve in five minutes.