Mastering Geotab
★ Geotab Harnesses · Make-Specific and Custom Harnesses
The HRN-CT20T11 is a Geotab custom harness that connects a GO9 telematics device to a 2019 or newer Tesla Model 3. It exists because the Model 3 has no standard OBD-II port for a plug-in tracker.
The HRN-CT20T11 is a short custom harness from Geotab that lets a GO9 device read data and draw power on a Tesla Model 3 built for model year 2019 or later. Tesla never gave the Model 3 the familiar 16-pin diagnostic socket under the steering column, so a tracker that simply plugs in on a gas pickup has nowhere to go here. This part bridges that gap: one end mates with the car's own connector, the other end presents a socket the GO9 recognises.
Fleets running Model 3 sedans as pool cars, sales cars or supervisor vehicles ask us for this part most often. The trick with Model 3 harnesses is that Geotab splits them by year, and the 2019 line is where this one starts.
Geotab lists this harness for Tesla Model 3 cars of model year 2019 or newer, and it names the GO9 as the device it requires. No replacement part, add-on base harness or kit contents appear in the listing, so on paper it is a single-piece order. The published length is 30 cm (12 in), and the identification table caps the full connected run at 2 m (6.5 ft).
Two neighbours matter here. Earlier cars, 2018 and back, take the HRN-CT20T1 instead. The redesigned Model 3 that arrived for 2024 is listed by Geotab under a separate kit, the HRN-CT06K1, together with the Model S, Model X and Plaid cars. We read the model year and body style before we order, never the other way round.
Our phones ring with the same story often: a company has added a handful of Model 3 cars to a fleet that is otherwise gas trucks, and the trackers that went into the trucks in ten minutes will not fit the Teslas. Without the correct harness, those cars become blind spots in MyGeotab, with no trips, no idle reports and no location history. The HRN-CT20T11 brings them into the same dashboard as everything else.
It also keeps the install clean. Because the harness is purpose-built, our technicians are not splicing into high-voltage-era wiring or guessing at pinouts on an electric car, which protects the vehicle and the customer's lease return condition.
We start with the car parked, in park, and fully stationary, since Geotab forbids installing or removing hardware on a moving vehicle. A typical sequence on the Model 3 runs as follows:
Geotab's general harness rules apply: no harness run on the car may exceed 2 m (6.5 ft) in total, and one T-harness must never be plugged into another.
| Spec | Detail |
|---|---|
| Part number | HRN-CT20T11 |
| Type | Custom harness, Tesla |
| Made in | China |
| Vehicle | Tesla Model 3, model year 2019 or newer |
| Required device | GO9 |
| Length | 30 cm (12 in) |
| Maximum connected cable length | 2 m (6.5 ft) |
The year split is the trap. A 2018 car and a 2019 car look almost identical from the curb, and ordering by appearance is how the wrong harness ends up on the truck. The tenth character of the VIN gives the model year (K means 2019), so we read it off the windshield plate before ordering. Watch also for the 2024 redesign, which Geotab routes to a different kit entirely. Once fitted, keep the GO9 away from airbag paths and pedal travel, and do not leave it hanging on the harness alone, since vibration works loose any connector that carries weight.
No. Geotab lists the HRN-CT20T11 for 2019 and newer Model 3 cars and assigns the HRN-CT20T1 to cars from 2018 and earlier, so the model year decides which one we order.
Geotab lists a GO9 as the required device for this harness, so a GO9 is what we pair with it. We do not fit it to other GO models unless Geotab publishes that support.
Geotab publishes a length of 30 cm, which is about 12 inches, and caps the total connected cable run at 2 m (6.5 ft).
API Signal brings the Geotab harness and GO9 to your yard and fits both on site, backed by 35 years of twelve-volt work. Tell us how many Model 3 cars you run and their model years, either by phone at 803-513-1009 or through our Get a Quote form.
Sources: Geotab Harness Identification and Application; Geotab blog: harness selection rules. GEOTAB is a registered trademark of Geotab Inc. API Signal is an independent installer and is not Geotab.
Tell us how many vehicles and what they are. We'll quote the hardware and the install together.