Troubleshooting 2018 Toyota Tundra Brake Controller Not Recognizing Connected Trailer

Products Featured in This Question

Tekonsha Prodigy P3 Trailer Brake Controller - 1 to 4 Axles - Proportional

(6342)

$139.94

10 Gauge Wire - Blue Primary - Per Foot

(101)

$1.86

Question:

2018 Tundra brake controller does not recognize trailer connected. Please let me know how to simulate trailer is connected so I can check if the brake controller is producing voltage. Is there a certain resistance range expected from the trailer brakes, or from trailer lights? In my case the trailer brake circuit has 3 ohms resistance. The trailer light circuit has very low resistance as the lights are LED. Could that be the problem? Thanks,

asked by: Scott B

Expert Reply:

The brake light circuit actually differs from the brake controller circuit. If you check out the linked photo you can see that the brake/stop light circuit is actually tied to the left and right turn circuits as well which as in the 3 and 9 o'clock positions on your 7-Way. Your brake controller circuit should be in the 5 o'clock position on your 7-Way.

If your brake controller isn't recognizing that a trailer is connected then that means the pin in the 5 o'clock position isn't sensing a connection. For example, the Prodigy P3 # 90195 sends back a pulse with a very minimal amount of current to "test" if a trailer is connected. If there is no connection there or the circuit for your trailer brakes is damaged on your trailer end then that would result in the "no trailer connected" signal you are reading.

You can test to make sure that your brake controller is sending power back to that 5 o'clock pin by using your tester to see if voltage is present when you set the controller to max power and use the manual override. If you don't see power then there is a connection missing on your 2018 Toyota Tundra. If you are seeing voltage then the problem is on your trailer and you need to check the wire connected to the opposite pin on your trailer connector.

Make sure your trailer 7-Way is clean and free of debris and corrosion and then move on to the wiring. Check for places where the wiring is damaged or pinched and replace with 10 gauge wire # 10-1-1. This should fix your problem.

expert reply by: Jon G

click to enlarge

Luke S.

3/8/2024

Hey mate why would my Indicator be coming on when I put my foot on the brake?

Jon G.

3/10/2024

@LukeS Is your trailer indicator blinking like it would if your turn signal is on, or are you just saying that the turn signals on your trailer light up as well as your brake lights on your trailer? Or is all of this happening on your vehicle side of things?

Luke S.

3/11/2024

@JonG Hey mate my indicators are going solid when my foot is on the brake only on the trailer but when I use my indactors as normal it works fine and even when I use tail lights they work normally what would cause that?

Jon G.

3/11/2024

@LukeS The vast majority of trailers have the stop and turn functions combined on the tail lights so that may be what's going on. If these functions are supposed to be separated out (as in, they used to work in this fashion) then it sounds like you might have a corroded connection or damaged wiring somewhere. Check all of your connections and connectors for anything that looks out of place or damaged and fix accordingly. It may also help to try connecting your vehicle to a different trailer and your trailer to a different vehicle just to help isolate which end of the towing setup is causing the issue.