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.
Continue Researching
- Search Results: butt connectors wiring
- Shop: Brake Controller
- Video: Installing the Redarc Tow-Pro Liberty Brake Controller on a 2018 Toyota Highlander
- Shop: Redarc Tow-Pro Liberty Brake Controller w/ Universal Wiring Harness - Dash Knob - Proportional
- Shop: Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires
- Video: Comprehensive Review: Universal Wiring Harness for Redarc Tow-Pro Trailer Brake Controllers
- Q&A: Troubleshooting Pre-Collision System Malfunction with Primus IQ Installed on a 2017 Highlander
- Shop: Trailer Wiring
- Shop: Roadmaster Single Park Light Diode
- Q&A: Parts Needed to Install Redarc Tow Pro In 2017 Toyota Highlander
- Video: Setting up the Universal Installation Kit for Trailer Brake Controller on a 2019 Toyota Highlander
- Q&A: Troubleshooting Pre-Collision Warning After Installing Brake Controller on 2018 Toyota Highlander
- Shop: Deka Heat Shrink Butt Connector - 12-10 Gauge - Nylon Insulation - Yellow - Qty 10
- Video: Installing the Redarc Tow-Pro Liberty Brake Controller on a 2017 Toyota Highlander
- Q&A: Which Color Wire is Brake Light Switch for 2017 Toyota Highlander for Installing Brake Controller
- Search Results: 331~tpsi~002
- Shop: Mounting Panel for Redarc Tow-Pro Trailer Brake Controller Control Knob
- Shop: Hook Probe Circuit Tester
- Shop: Universal Wiring Harness for Redarc Tow-Pro Trailer Brake Controllers
- Search Results: pk12711u
- Shop: Vehicle Tow Bar Wiring
- Search Results: 10~2~1
- Q&A: 7-Way Trailer Wiring Connector Recommendation for 2018 Toyota Highlander
- Q&A: Finding the Cold Side of the Stop Light Switch on a 2017 Toyota Highlander
- Video: The Low-Down on the Roadmaster Single Park Light Diode
- Search Results: dw05745~5
- Search Results: red52vr
- Search Results: 22119
- Video: How to Install: Roadmaster Single Park Light Diode on your 2003 Jeep Wrangler
- Video: How to Install the Roadmaster Single Park Light Diode on a 2016 Hyundai Elantra
on Trailer Brake Controller
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).