I recently installed a hitch on my 2015 Transit 350 HD cutaway with a Reading utility box on the back. The truck came from the factory with the "tow package". I got a harness from Ford
(part# CK4T-13B576-KB) and wired it to the combo 4 pin- 7 blade trailer plug. The LED step I installed & plugged into the 4 pin on the receiver hitch works fine until I activate either turn signal. It will then intermittently blink very fast. Any idea's on how to fix this problem? Maybe a different flasher relay? If so can you identify the exact location on my vehicle?