Troubleshooting A Tekonsha Primus IQ That Back Feeds Power When The Manual Override Is Used

Question:

I have a 2018 Toyota Highlander and followed your direction to install a 7 pin system and a brake controller but I am as well getting a pre-collision malfunction error if i press on the manual trailer brake switch. I noticed in another QandA that this is caused by back feed of power into the car brake system and to install a 1 amp diode. Is this the same process for me to fix the issue? And to clarify you just need to splice in the diode between the red wire coming out othe controller and going to the brake signal? I have a Tekonsha Primus IQ controller. Is there other controllers you can use that dont require the aftermarket diode?

asked by: D S

Helpful Expert Reply:

If power is back feeding from the unit out to the brake light switch wire then it's likely an issue the brake controller itself, but using a diode, like part # RM-690, on the red wire between the Tekonsha Primus IQ # TK90160 and vehicle wiring would help eliminate the back feeding. Since this isn't common there isn't a list of brake controllers that need or do not need an additional diode to prevent back feeding.

expert reply by: Kevin C