How To Diagnose 4-Way Trailer Wiring That Only Has Running Lights On 2020 Ford Ecosport

Question:

Hooked up to 2020 Ecosport Titanium just like in your video only getting running lights no brakes or turn signals. What could be wrong fuse and power line good.

asked by: David G

Expert Reply:

If you do not already have one, it would be a good idea to get a 4-pole tester such as the Curt LED 4-Way Flat Connector (Vehicle End) Tester # I26. Using this tester, you can verify if the vehicle wiring is working properly.

If the 4-pole tester verifies that you are having issues at the vehicle end, not trailer end, then make sure all of the connections are good on the vehicle's trailer wiring kit using a circuit tester like the Circuit Tester Kit # PTW2993.
Verify the ground wire (usually white with a ring terminal) is firmly attached to bare metal on the vehicle. Examine the wiring and connections at the vehicle taillight housing on both passenger and driver side, making sure there are no wires getting pinched anywhere.

Once the vehicle side checks out good, check to see if the trailer lights are now functioning properly. If not, then you know the issue is within the trailer wiring.

Using a circuit tester, make sure you have a good ground connection on the trailer. You also need to verify that your 4-Pole trailer connector is wired the same way as the vehicle side 4-Pole connector. You may need to check each wire on the trailer to see where there might be a bad connection, or you may need to re-wire the trailer using a trailer wiring kit such as the 35 Ft 4-Way Trailer Wiring Harness # A35W42B.

I have attached a few videos that may help out with the diagnostic process.