877-433-7847 Online Catalog Order History Additional Resources Login Register Invoice Reprint Contact Us Product Catalog Table of Content Diagnostics Trailer Wire Harness Test Tools ItemItem NumberDescriptionPriceAdd To Cart HOP50918 Tow Doctorâ„¢ Circuit Tester - Vehicle Side $356.16* * log in for dealer pricing. Add To Cart HOP50928 Tow Doctorâ„¢ Circuit Tester - Trailer Side $680.96* * log in for dealer pricing. Add To Cart TLT5 Trailer Hitch Wire Harness Tester (4 and 5 Pin) $38.08* * log in for dealer pricing. Add To Cart Notice: