Mastering Geotab
★ Geotab Harnesses · Make-Specific and Custom Harnesses
The HRN-CW08K4 is Geotab's custom 8-wire harness kit for vehicles that have no supported diagnostic connector, wiring a GO device straight to power, ground and the vehicle's data networks. It works through the HRN-CM24Y1-A base harness.
The HRN-CW08K4 is a custom 8-wire harness kit that lets a GO device read a vehicle that has no supported plug-in connector, by wiring directly to the vehicle's power, ground and data network lines. The kit holds the 80 cm (31 in) harness and a fuse kit, and it connects to the GO device through the HRN-CM24Y1-A base harness, which Geotab lists as a requirement.
This is the harness for the vehicles that fall through every other category: a truck body with an unusual diagnostic setup, specialty equipment, or a vehicle where the factory connector is missing or unsupported. Geotab's install document sets the minimum for it to work: power, ground and at least one data bus must be connected.
Geotab's definition is simple: vehicles without supported connectors. Its install document adds that the installer needs real technical skill for off-road equipment, citing Certified Geotab Installer status or an equivalent.
The data side of the harness covers several network types. The blue and white pair handles J1939 or CAN high and low. The brown and green pair handles J1850 or J1708. Orange and grey are the ISO K and L lines. Geotab notes that K and L lines without labels need interface information from the vehicle's manufacturer before they can be used.
On the device side, the HRN-CW08K4 always runs through the HRN-CM24Y1-A, whose ALDL connector takes the GO device.
Without this kit, a vehicle with no usable port leaves a fleet two weak choices: a GPS-only power install with no engine data, or no tracking at all. The 8-wire kit offers a third option by reaching the data networks directly, so hours, faults and engine readings can be captured where the vehicle broadcasts them.
It is also a job that rewards experience. With 35 years in twelve-volt work, our technicians are comfortable finding and proving a data pair on an unfamiliar wiring harness, which is the heart of this install.
Geotab's document starts with a safety step: disconnect the GO device from the vehicle before installing the harness or any IOX, and reconnect it only when the wiring is complete. The vehicle stays parked and switched off throughout.
The core of the job is identifying the networks. Data pairs are usually twisted, at roughly one twist per inch (25 mm). If the wires are not labelled, measure DC voltage to ground with a digital meter. Geotab gives typical readings of about 2.5 to 3.0 V on CAN high and 2.0 to 2.5 V on CAN low, and about 3.0 to 4.5 V on J-bus positive and 0.5 to 1.5 V on J-bus negative. Exact values vary; what matters is that the positive line reads higher than the negative one. To confirm a CAN pair, disconnect the battery and measure resistance across the two lines, looking for about 60 ohms.
Connect red to the power source through the supplied fuse kit, black to a sound vehicle ground, and at least one data pair to its matching lines. Plug the harness into the HRN-CM24Y1-A, connect the GO device, and fasten everything with cable ties. Geotab's harness limits still apply: 2 m (6.5 ft) total connected length, and never two T-harnesses linked together.
For verification, Geotab's document has the installer enter the installation details at installmygps.com, then start the engine and let it idle. The unit beeps for about five minutes while it updates; the LEDs flash red briefly and then settle with red, green and blue all lit for power, cellular and GPS. The GPS antenna on the bottom of the device must face skyward. We finish by checking the asset in MyGeotab for engine data, not just location.
| Spec | Detail |
|---|---|
| Part number | HRN-CW08K4 |
| Type | Custom 8-wire harness kit |
| Kit contents | 8-wire harness and fuse kit |
| Length | 80 cm (31 in) |
| Requires | HRN-CM24Y1-A base harness |
| Minimum connections | Power, ground and at least one data bus |
| Networks supported by wiring | J1939/CAN, J1850/J1708, ISO K-line and L-line |
| Installer requirement | Professional installation; Certified Geotab Installer or equivalent for off-road equipment |
| Max connected cable length | 2 m (6.5 ft) |
| Country of origin | China |
Prove every data pair with the meter before splicing, and never take wire color on the vehicle side as proof; Geotab's figures say "usually" for a reason. Remember the battery must be disconnected for the 60 ohm test. Unused data wires should be insulated and tied back so they cannot short. Seal every splice, because a corroded data tap causes dropouts that look like device faults. Leave the GO device unplugged until all wiring is done, as Geotab instructs.
No. Geotab lists the HRN-CM24Y1-A as a requirement, and it is the part the GO device actually plugs into.
Geotab's document requires power, ground and at least one data bus. The remaining data wires are used only where the vehicle has those networks.
Look for a twisted pair, measure DC voltage to ground so the higher line is identified as positive, then confirm about 60 ohms across the pair with the battery disconnected.
When a vehicle has no supported connector, API Signal supplies the HRN-CW08K4, the base harness and the GO device and wires them on site at your yard, data pairs proven with a meter. Get in touch at 803-513-1009 or describe the vehicle in Get a Quote.
Sources: Geotab Harness Identification and Application, Geotab HRN-CW08K4 installation document, Geotab HRN-CW08K4 support document. GEOTAB is a registered trademark of Geotab Inc. API Signal is an independent installer and is not Geotab.
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