Installing a Brake Controller on a 2005 Toyota Tacoma Without Brake or 12 Volt Power Wire  

Question:

Expert Reply:

I am surprised to hear your 2005 Toyota Tacoma came with the factory brake controller harness, but the 7-way trailer connector was not wired for brakes or 12 volt power. If you were not the original owner, it may be possible that the previous owner had the 7-way connector installed, but only had the light functions wired.

There is really no telling where Toyota stopped the power wire and brake wire from the brake controller harness under the dash. Unfortunately there is not a specific place on the Tacoma where these wires can be found. You may be able to trace the wires from the brake controller connector, but you may lose them when they pass through the firewall.

There are a few different options that you have. First, I recommend testing the factory brake controller connector under the dash to see if it is active. Use a circuit tester, like part # PTW2992, to test the pins in the connector. With the truck on, one pin should have constant 12-volt power and another pin should show power only when the brake pedal is pressed. If you have a pin with 12-volt power and a pin with power with the brake pedal, then you can use Custom Wiring Adapter, # 3040-P, and we will only have to run a wire for the electric brake output wire and the 12-volt power wire for the trailer connector.

To run the additional wires, you will want the Brake Controller Wiring Kit, # 5506. This kit includes all of the wires and hardware needed to complete the installation. The duplex wire in this kit contains a black wire and a white wire. Run the black wire from the 7-way trailer connector to the positive post on the vehicle battery via the included 40-amp circuit breaker. Run the white wire from the 7-way trailer connector into the cab of the truck and connect that to the blue brake output wire coming from the brake controller. You can splice it into the blue wire before or after the factory connector.

If the factory brake controller connector under the dash is not active, then you will still want the Brake Controller Wiring Kit, # 5506, but you will not need the Custom Wiring Adapter, # 3040-P. Instead, you will use the universal wiring adapter that comes with the brake controller. You will follow the same steps that I listed above, but you will also need to run a 12 volt power wire from the vehicle battery post into the cab via the included 20-amp circuit breaker and connect it to the black wire from the brake controller. You will want to ground the white wire from the brake controller and the red wire will connect to the cold side of the stop light switch.

The stop light switch is located at the top of your brake pedal. You will see a white plastic connector with 4 or 5 wires coming out. Use the circuit tester to probe the wires to find which wire only has power when the brake pedal is pressed. Traditionally, Toyota used a blue wire for this, but vehicle manufacturers have been known to change their wire color from time to time. I have attached a brake controller installation video on a 2008 Toyota Tacoma that covers this type of installation for you to check out. I have also attached a few help articles on brake controllers and installation for you to check out as well.

If you have any questions about specific steps, feel free to send me an email.

expert reply by: John H

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