Troubleshooting Curt T-Connector C56353 On 2020 Toyota Prius W/ No Trailer Running or Brake Lights

Question:

I bought the recommended Item # C56353, for my 2020 Toyota Prius. I installed per the instructions. The left and right turn signals work correctly, however, the Prius brake lights function, but do not engage the trailer brake lights. There are also no running lights working on the trailer. I used a different vehicle to make sure that the trailer brake lights are indeed functioning. The t-connectors are all secure and clipped together correctly. Any help on getting the trailer brake lights to work correctly w/ the 4-pole connector would be greatly appreciated.

asked by: N. A

Expert Reply:

I am sorry to hear you ran into an issue with the Curt T-Connector Vehicle Wiring Harness # C56353 you purchased for your 2020 Toyota Prius FWD.

Since the issues you are having are the brake lights and the running lights, and both of those circuits get power from the grey connectors on the harness I recommend double checking that those connectors are connected correctly and securely.

If they are then you will want to use a circuit tester like # PTW2993 to test the red and brown wire going into the module. If there is not power going into the module remove the two connectors and look for any bent pins or debris that may have gotten into the connector, and double check that the white ground wire is secured.

If you do have power going into the module on these wires but no running lights or brake lights on your trailer then the module has an internal issue and will need to be replaced.

Let me know what you find and I would be happy to go into more in-depth troubleshooting if needed.

I included a video of the # C56353 being installed for you to take a look at.