Troubleshooting Pre-Collision System Malfunction with Primus IQ Installed on a 2017 Highlander

Question:

I got the Tekonsha Primus IQ brake controller for my 2017 Toyota Highlander. When I apply just the trailer brake with the slide switch, I get an error message on the Toyota Pre-Collision System Malfunction.

asked by: Mike H

Expert Reply:

I spoke with my contact at Tekonsha who knew exactly what you were talking about.

He said that the best solution for installing a brake controller like the Primus IQ # TK90160 in your 2017 Toyota Highlander is to install a diode on the red wire of the wiring harness for the Primus IQ. This is the wire that connects to the cold side of the stop light switch.

To prevent the 12V from backfeeding into your Pre-Collision System he recommended using a diode rated for 1 amp. These are not very common so you may have to do a little searching to find one.

expert reply by: Jon G