The details
- The P3 (Tekonsha model 90195) uses the same controller-side two-plug connector as the Prodigy P2 and Primus IQ. Any harness that fits one of those fits all three.
- Tekonsha sells custom harnesses by vehicle family. For example, one part number covers many Toyota and Lexus trucks and SUVs (4Runner, Tacoma, Tundra, Sequoia, Land Cruiser and related Lexus models), another covers Ford, Lincoln, and Mercury applications, and GM, Ram, Jeep, and Nissan each have their own numbers.
- The vehicle end plugs into the OEM brake-controller port, usually tucked under or behind the dash near the steering column or kick panel. That port is present when the vehicle has factory tow-package wiring.
- If your vehicle has no port, the P3 ships with a hardwire pigtail: four wires (battery power, ground, brake output, and stoplight signal) that get run to the battery through a circuit breaker and spliced at the brake switch.
- Match the harness by model year, not just make. The same truck line can switch connector styles between generations, so a harness that fit a friend's older truck may not fit yours.
How to find the right one
Do it in this order and you will not buy twice:
- Check under the dash for the factory brake-controller connector first. No connector usually means no tow-package wiring, which means hardwiring.
- Run your exact year, make, and model through Tekonsha's fitment guide or a reputable towing retailer's lookup. Do not shop by connector photo alone, since several OEM plugs look similar but are keyed differently.
- Confirm the listing says it fits Tekonsha two-plug controllers. Harnesses for other brands' controllers can use different controller-side plugs.
The trap to avoid
The 7-way socket at the rear bumper is not the brake-controller port. Having a 7-way does not guarantee the under-dash connector exists, and some vehicles have the port but no relay or fuse installed for the brake output circuit. Owners routinely plug everything in, get a working display, and then find the trailer brakes are dead because the tow-package fuses were never populated. Check the fuse box against the owner's manual before assuming the harness is at fault.
Also note that many late-model trucks ship with a factory-integrated brake controller. If your dash already has trailer-brake gain controls, you do not need a P3 at all.
What owners actually do
The common path in owner communities: buy the P3 and the vehicle-specific harness together as a bundle, plug the harness in at the port, mount the P3 bracket under the dash, and test on a lit trailer before the first trip. People who hardwire generally report it is a one-evening job, with the circuit breaker at the battery being the step most often skipped and most often regretted.