The dealer should have done their homework before trying to put this on. The 2020 vehicle harness is missing a couple wires. You probably overpaid for that 7-pin harness and don’t want to cut into it. If I were you I would try to get a refund. A universal 7-way RV connector is what you need. (You might have a 7-way round connector)
You just need a wire run to the battery with an inline auto resetting breaker to get 12v+. But you will also need a 4-pin plug and play harness to plug into the back of the universal 7 pin and you’ll need to tap into the reverse which is pin #8 on the connector. Then you will be all set to run the Prodigy RF. Since you are using this brake controller there is no need to run a wire through the firewall into the cabin.
The story of installing a 7-way connector on a 2020 Telluride
Pinout Reference:
Trailer Wiring
You can buy the Kia 4-pin flat that was made for the 2020 to plug behind the 7-pin universal, but it’s pricier than the Curt and Tekonsha that are $34-42 and are also designed for the Telluride. The Curt is the one to go with in my opinion because it’s rated for higher amperage, 7.5A on the tail lights, than the Kia one, 5.5A on the tail lights. The lower amperage Kia one could be a problem if you have more older lighting that you need to power on what you are towing.
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Any travel trailer dealer should be able to do this for you.
If you don't want to deal with the dealership that installed incorrectly for the Prodigy RF, here is one option. It's possible you have the 12V on a different pin and it just needs to be moved. You can confirm what connection you need here:
https://storage.googleapis.com/curt.../Complete_Trailer_Wiring_Color_Code_Chart.pdf (
Source)
If you don't need the reverse/backup connection and all you need is a 12V+ from the battery, you simply need a 10ga or 12ga wire run from the battery to an auto reset 30A circuit breaker mounted near the battery, then continue the wire along the underneath of the vehicle back to the 7-way you already have going to the correct pin.
I'm not sure where that diagram came from but since the pins are small colored rectangles, it implies that it's a 7-way RV blade, but I'm pretty sure Kia sells a 7-way round. You might actually have 12V but that's not the right pin. The images I've seen of the Prodigy RF Brake controller show a 7-way RV connection.
Lastly, if I'm completely wrong about your dealer and they actually properly configured your 7-way round with 12V+, then you might just need an adapter to go from 7-way round to 7-way blade. Most places will sell you a Hopkins 48485 adapter and that could be all you need.
