I Live in Hilly Scranton PA, put a hitch and a small trailer to tow a small Motorcycle 100 Miles down I 81 and 61 to Reading, PA. . Got about 30 MPG but engine seemed to have the or a brake on up and down hills. This package could not have been 500 lbs behind the car. When I got home, disconnected trailer and lights and ran normal. Than I hooked the trailer up BUT DID NOT hook the lights up and it seemed to run much better. DID not seem to have the earlier "DRAG". .When I came back after delivering the 200 lb motorcycle still seemed a drag up and down hills. There was no indication on the dash that anything was wrong. It was like there was a engine/ electrical problem. Evan down some long hills you would think the trailer would "Push" you to higher mileage. but no.....??? When I got the hitch put on, and gave the garage the wire hookup kit, no problem was said to me, but I noticed that I had to reset the clock and some gauges. Could it be that the new Wire Harness for the trailer, if connected wrong, for the trailer screwed up the computer??? COULD this be possible... ALso How do I reset the CLOCK>
I don't know the finer details of the Prius electrical system, but it sounds like the brake light hookup somehow activated the regenerative brakes.
I've put hitches on various cars I've owned over the years, but for the most part they've always turned to be a bit of a drag! (sfx: rim-shot!)
Have you considered checking the wheels on the trailer to be sure they are turning free ?? Aside from that, I think it's all in your head. But yes, they probably DID disconnect the battery while doing the electrical work and that will reset various computer memory parameters and might make the car drive a bit differently for a few days. Having the trailer hooked up during those first few days might complicate matters.
