Tekonsha Primus IQ Trailer Brake Controller: What It Does and How to Decide
Immediate answer
The Tekonsha Primus IQ is a proportional electric trailer brake controller intended for vehicles towing trailers with electric brakes. It applies trailer braking force in proportion to how hard the tow vehicle is slowing, rather than using a simple time-delayed ramp. The main condition that changes the recommendation is installation wiring: the Primus IQ generally requires a vehicle-specific plug-in harness or a hardwire connection, and it is not designed for trailers with electric-over-hydraulic brake systems unless an additional adapter is confirmed for the setup.
What proportional braking means
A proportional controller uses an internal sensor to detect the tow vehicle's deceleration. When you brake gently, the trailer brakes receive gentle output. When you brake harder, the trailer brakes receive stronger output. This differs from time-delayed controllers, which apply a preset amount of braking after a short delay regardless of how firmly the tow vehicle is stopping.
Vehicle compatibility
Compatibility is tied to the specific model year, market, trim and factory towing package of the tow vehicle. The Primus IQ connects to the vehicle through either a model-specific plug-in brake control harness or a universal hardwire setup. Vehicles with a factory trailer brake controller port are generally easier to install, but the port location and required adapter vary by vehicle. Before purchase, confirm whether the tow vehicle has a factory brake controller connector and whether a compatible harness is available for that exact year, trim and wiring configuration.
Trailer brake compatibility
The Primus IQ is intended for trailers with electric drum brakes. It is not a direct controller for electric-over-hydraulic brake systems. If the trailer uses electric-over-hydraulic actuation, check whether the brake system manufacturer allows a standard proportional electric brake controller to drive it through a compatible interface. Do not assume compatibility based only on the trailer having a seven-way connector.
Installation and adjustment
Installation requires a solid electrical connection to the vehicle brake switch signal, battery power, ground and the trailer brake output circuit. On vehicles without a plug-in port, the installer must identify the correct cold side of the brake light switch and route fused power from the battery. The Primus IQ has a manual override lever and gain adjustment. Initial setup usually involves setting the gain low, driving at low speed, and increasing it until the trailer brakes engage firmly without locking on a dry surface. The correct setting can change with trailer load, so adjustment is not a one-time event.
Ownership trade-offs
Advantages: • Proportional braking feels more consistent with the tow vehicle than time-delayed control. • Manual override lets the driver apply trailer brakes independently when sway starts. • Works with common electric drum brake trailers. Limitations: • Needs vehicle-specific wiring or careful hardwiring. • Not a direct fit for electric-over-hydraulic systems without confirmed adapter support. • Gain may need adjustment when trailer load changes significantly.
Common questions
Does the Primus IQ fit my truck? Fitment depends on the vehicle connector and available adapter, not just the brand. Check the specific model year, trim and towing package before ordering a harness.
Can it control disc brakes on a trailer? Electric drum brakes are the standard match. Some electric-over-hydraulic disc brake systems may accept a proportional controller through a compatible interface, but this must be verified with the brake system or trailer manufacturer.
Why does the display show an error or no output? The likely causes are a missing brake signal, poor ground, incorrect harness pinout, or a short in the trailer brake circuit. Because the harness and vehicle connector vary, wiring is the first thing to inspect when output is absent.
Information gaps
Specific mounting dimensions, harness part numbers for every vehicle, exact vehicle fitment years, and current pricing are not supplied here. Availability and adapter part numbers should be confirmed with the retailer or vehicle fitment guide for the exact model year and trim. No performance measurements or firsthand towing results are stated.
Bottom line
The Tekonsha Primus IQ is a practical proportional brake controller for electric trailer brakes when the tow vehicle has the correct wiring path or available plug-in harness. If the trailer uses electric-over-hydraulic brakes or the vehicle lacks a clean brake signal connection, confirm compatibility before purchase rather than treating the controller as universal.