1999 Honda Odyssey with an OEM 4-pin extension plugged into the car's built-in pre-wired trailer-light takeoff (behind right rear trim panel near taillight). A 4-Pin test device and a circuit tester both indicate all 3 functions (brake, tail and turnsignal lights) work correctly at the plug where the trailer connects.
I have tried 4 different trailers whose lights I know are good and on every one ONLY the tailights work... no turn signals and no brake lights. Yet the tests on the carside plug indicates all works OK.
I have rewired, I have emory-clothed all connections to their shiniest... all to no avail.
I'm a ticket waiting to happen. Can anyone suggest what may be the cause of the problem?
Many Thanks