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Technical · Free Excel and Word pack

CAN / FMS interface commissioning record

The tracker is on the bus. Does it read the right rate, without warnings, and do its numbers match the dashboard? Measure, compare and sign once per vehicle.

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Free: enter your name and email and we send you the files. Excel workbook and Word field record. No macros.
  • FMS, J1939 and OBD-II points
  • Termination diagnosis
  • Seven common J1939 parameters
Follow the vehicle maker guidance

A wrong connection on a vehicle bus can set warnings or disturb other units. Use the connection point the vehicle maker allows, a listen-only setting where the device offers one, and disconnect at once if a warning appears. The record documents the work. It does not make a connection safe.

What's inside

From the connection point to the signature

For installers and integrators who connect a tracker or FMS reader to trucks, buses and machines, and for the fleet that accepts the work.

  1. 01

    Start

    Vehicle, VIN, connection point, pins, device, firmware and the listen-only setting.

  2. 02

    Limits

    Typical termination bands, the rate × length rule and your parameter tolerance. All editable.

  3. 03

    Measurements

    Eight readings, each with a result and a plain-language meaning.

  4. 04

    Parameters

    Seven common J1939 parameters with PGN and SPN, seen or not, and the difference to the dashboard.

  5. 05

    Summary and Word record

    A suggested decision, a punch list, two signatures, and a two-page field record.

The first reading

One ohmmeter reading says a lot

With the power off, the resistance between CAN-H and CAN-L shows whether both ends of the bus are terminated. The workbook turns the reading into a result and a meaning.

120 Ω120 ΩEngine ECUDashboardTrackerCAN-HCAN-LPower offH–L ≈ 60 Ω
Fig. 1 Two 120 Ω terminators in parallel read about 60 Ω between CAN-H and CAN-L with the power off.
Termination reading, power off (typical bands)
Reading CAN-H to CAN-LWhat it usually means
Two terminators, normal50 – 70 Ωtypical
One terminator may be missing100 – 140 Ωtypical
Extra terminator or short< 50 Ωtypical
Broken wire or no terminator> 140 Ωtypical

Typical bands. Replace them with your procedure or vehicle document.

max length (m) = 50 ÷ bit rate (Mbit/s)Example: 50 ÷ 0.25 = 200 m at 250 kbit/sA rule of thumb from TI application note SLLA270. Your vehicle document wins.
Parameters preview

Seen is not the same as right

A parameter the device sees can still be scaled wrong. Compare it with the dashboard or a meter at the same moment. Difference = |platform − reference| ÷ reference.

tracom-can-fms-commissioning-record-en.xlsx
ParameterPGNSPNSeen?PlatformReferenceDifferenceResult
Engine speed61444190Yes6526500.3%Pass
Total vehicle distance65248245Yes1824501823000.1%Pass
Fuel level6527696Yes415018.0%Check
Engine total fuel used65257250NoFail
Example values. Fuel level differs by 18 percent from the gauge, above the 2 percent tolerance, so it shows Check. Total fuel used is needed but not seen, so it fails.

Why a commissioning record

Most CAN problems show up weeks later: a fuel graph that drifts, engine hours that stop, a warning lamp the driver reports. Without a record of how the device was connected and what it read on day one, nobody can tell whether the vehicle changed or the installation was wrong.

Connection points

The record lists the usual options. Write the one you used and the pins or wires.

  • FMS gateway or interface
  • J1939 9-pin diagnostic connector (pins C and D)
  • OBD-II connector (pins 6 and 14)
  • Direct tap on the CAN pair
  • Contactless CAN reader

On the J1939 9-pin connector, CAN-H is pin C and CAN-L is pin D. On OBD-II, CAN uses pins 6 and 14. Many trucks and buses offer an FMS gateway that separates the reader from the vehicle bus: use it where the vehicle maker provides one.

The measurements

Resistance first, with the power off. Then the bit rate: the device must use the same rate as the bus, commonly 250 or 500 kbit/s on J1939. Then the bus length against the rule of thumb, the voltages with the ignition on, and two plain checks: the platform shows CAN data, and the dashboard shows no new warning.

The voltage limits start empty. Common textbook values exist, but we could not confirm them from a source we can cite, so enter yours from the vehicle or transceiver document. Until then the rows show Recorded.

Checking parameters

Mark the parameters the fleet needs. For each one, note whether the device sees it and compare the platform value with the dashboard or a meter at the same moment. A difference above your tolerance shows Check: look at the scaling and the source before you accept it.

Not every vehicle sends every parameter, and some send them only through an FMS gateway. A Fail on a parameter the vehicle does not send is a fact to record, not a fault in the device.

Limits and sources

Termination, length and rate: TI application note SLLA270 and the CSS Electronics CAN introduction. J1939 rates, pins and the PGN example: the CSS Electronics J1939 introduction. Checked 2026-10-31. The 250 and 500 kbit/s rates match the titles of SAE J1939-11 and J1939-15 (250 kbit/s) and J1939-14 (500 kbit/s) at sae.org, last checked 2026-11-03. The pin letters and the termination values come from these secondary sources, because the SAE and ISO texts are not free to read. The other PGN and SPN numbers are common examples to confirm in your vehicle document.

The record documents a connection and a test. It is not a certificate or an approval, and it does not replace the vehicle maker guidance.

Related Tracom solution

Commission the CAN link on a Tracom device

Connecting Tracom ST100 or M1N to a truck or bus? Use the record during the installation, then check each parameter on your platform and keep the configuration file with the record.

  • Advanced configuration files. Keep the file you loaded with the record.
  • SCMS portal. Review the unit and its setup in one place.
  • Over-the-air update. Change a setting without a second visit.
Questions

CAN commissioning questions

Connecting to a truck bus? Talk to Tracom.

What reading should I see between CAN-H and CAN-L?

About 60 Ω with the power off, when both ends of the bus have a 120 Ω terminator. About 120 Ω usually means one terminator is missing.

Which bit rate does a truck use?

J1939 commonly uses 250 or 500 kbit/s. Take the value from the vehicle document, then set the device to the same rate.

Why are the voltage limits empty?

We did not find a citable source for them. Enter a verified range from your vehicle or transceiver document, or leave them as Recorded.

Are the PGN and SPN numbers right for my vehicle?

Not necessarily. They are common J1939 examples. Confirm each in your vehicle or FMS document.

A parameter is not seen. Is the device faulty?

Not necessarily. The vehicle may not send it, or only through an FMS gateway. Check the rate, the connection point and the vehicle document first.

What is Tracom's role here?

Tracom makes the devices. The record is a neutral template for any installer. It gives no approval and does not replace the vehicle maker guidance.

Next step

Record the CAN link on day one

Send us the vehicle make and model and the parameters you need. We will tell you what to check at the connection point.

Contact Us Get the record
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