Mastering Geotab
★ Geotab Harnesses · Special Order, European and Accessories
The HRN-UD03S9 is a 14-foot extension cable for the Geotab IOX-RS232D, carrying the module's 3-pin Delphi serial connection to third-party equipment mounted well away from the GO device.
The HRN-UD03S9 is a 14-foot (420 cm) extension cable built for the Geotab IOX-RS232D, the serial interface module that lets a GO device exchange data with other equipment on the vehicle. Geotab's description is brief: it is an extension cable used with the IOX-RS232D. The detail that matters for planning comes from the RS232 module documentation, which places it in a family of extensions that all use the 3-pin Delphi connector and expose only the receive and transmit data lines.
It is the longest of that family. Geotab lists 6 ft, 8 ft and 10 ft versions alongside it, so the S9 is the one chosen when the serial device sits at the far end of a cab, in a rear compartment or on an upfitted body.
Geotab publishes little about this part beyond its length, use and connector, so the rest of this page pairs those facts with the field checks we run before ordering a cable this long.
The extension pairs with the IOX-RS232D specifically. Geotab makes three RS232 modules: the F and M versions end in standard DB9 female and male connectors, while the D version is aimed at OEM setups that use a Delphi automotive connector and ends in an Aptiv 3-way male plug. The D module itself is about 1090 mm long; the HRN-UD03S9 adds 14 ft to that reach.
On the D connector, Geotab assigns black to ground, purple to receive and green to transmit. The extension carries the same 3-pin connection through. It is not tied to one vehicle type, because what it serves is whatever third-party serial equipment the fleet has fitted. Geotab lists it as made in China.
The GO device usually lives near the diagnostic port under the dash, but the equipment it needs to talk to often does not. Serial devices on work trucks, such as controllers and readers fitted by upfitters, are mounted where the operator uses them, which can be the far side of the cab or out in a body compartment. Geotab notes that the IOX wire length limits where the accessory can go. When the module's own cable will not reach, this extension closes the gap without cutting and splicing the serial lines.
A clean, plug-together extension is also easier to service later. If the third-party device is replaced, the cable stays and the new unit plugs in.
The sequence below follows Geotab's IOX-RS232 installation steps with the extension added:
| Spec | Detail |
|---|---|
| Part number | HRN-UD03S9 |
| Use | Extension cable for IOX-RS232D |
| Length | 420 cm / 14 ft |
| Connector | 3-pin Delphi |
| Signals carried | RX and TX only |
| Other lengths in family | HRN-UD03S6 (6 ft), HRN-UD03S7 (8 ft), HRN-UD03S8 (10 ft) |
| Country of origin | China |
The red and black leads on the RS232 module are powered whenever the GO device is on, and Geotab is firm that they may only feed a third-party device, never vehicle power. Leave the termination shunt in the last IOX in any chain and tie it in place, or other modules can lose communication. Total IOX current from a GO9 is capped at 2750 mA, so count every module and any device powered through it. A 14 ft cable needs a protected route: keep it out of seat tracks, door jambs and anywhere cargo can crush it, and avoid tight bends at the connectors.
Geotab lists it for the IOX-RS232D, the variant with a 3-pin Delphi connector. The M and F versions use DB9 connectors, and Geotab does not list this extension for them.
Yes. Geotab lists the same 3-pin Delphi extension in 6 ft (HRN-UD03S6), 8 ft (HRN-UD03S7) and 10 ft (HRN-UD03S8) lengths. We measure the actual route before choosing, so there is no large coil of spare cable to hide.
Geotab says the extensions expose only the RX and TX data lines on the Delphi connector. The IOX-RS232D has separate red and black leads that can power the third-party device, and those must never be tied to vehicle power.
API Signal supplies and installs Geotab harnesses and devices on site at the customer's yard, including IOX add-ons and the cabling that connects them. Call 803-513-1009 or use Get a Quote to plan an IOX install.
Sources: Geotab Harness Identification and Application, Geotab IOX-RS232 support document. 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.