Pre Collision Warning Error After Brake Controller Install on a 2017 Toyota Highlander
Updated 05/14/2025 | Published 07/25/2018
Question:
I am seeing the pre collision error with a Reliance brake controller installed on a 2017 Highlander. You posted solution here https://www.etrailer.com/question-277968.html For a different controller. Is the solution the same for a reliance controller? If so which wire do I attach the diode to on the controller? Red wire?
asked by: Jeremy
Expert Reply:
The Collision System Malfunction error message that you are experiencing on your 2017 Toyota Highlander after installing the Hopkins Reliance Trailer Brake Controller is a result of power backfeeding on the stop light switch wire into the collision system. In order to eliminate this you are going to need to install a 1 amp diode on the red wire between the brake controller and vehicle's wiring harness. This will then prevent power from backfeeding and allow you to use the Reliance on your vehicle without the error message.
Unfortunately, we do not carry the 1 amp diode so you need to source this elsewhere.
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Zachariah
5/8/2025
I found a youtube video where someone had a similar issue with a RAV 4. In the comments, someone said "Orient the diode so that the anode (the end with the white band) is toward the controller". From my personal knowledge, that would force the signal (voltage) to go only FROM the brake controller (kinda like a one-way road), as Jeremy has stated. On top of just the pre collision warning error, I had a 370mA parasitic draw. Installing the diode fixed both issues. The diodes that I purchased: pack of (5) 1N4001 diodes, which are rated for 1A, 50V. Hardware from etrailer that I installed: Tekonsha OEM Replacement Vehicle Wiring Harness w Brake Controller Adapter - 7 Way Trailer Connector 22119 Redarc Tow-Pro Liberty Brake Controller w/ Universal Wiring Harness - Dash Knob - Proportional RED52VR My vehicle: 2017 Toyota Highlander Hybrid I hope this can help someone. I spent HOURS troubleshooting and researching (for the parasitic draw).