I'm almost finished setting up 2007 HHR as TOAD. I purchased a Trailer Mate wiring harness TM 780039
which does not require any splicing into factory wiring. Install went long but okay. Then I had the question of a brake light relay since I was going to use a Brake Buddy which PUSHES on the car's brake pedal. The issue was the pushing on the brake pedal would override the TURN SIGNAL
command from the motor home when braking. ETrailer was contacted, said I needed a brake light relay so I ordered Roadmaster RM-88400 from them. I had already
installed Roadmaster RM-76511 fuse by-pass switch. I had some of the lower dash removed and was ready to cut into the car's brake light switch wiring when a bell went off in the brain. I turned the ignition to accessory, turned the switch OFF for#8 fuse
and discovered that this action still allows the high mounted stop light to function but the round combination brake/tail light fixtures do NOT
have brake light function from the car's pedal. I made an extension harness and tested this numerous times in the garage and the turn signals from the towing vehicle work just fine with the TOAD brake pedal depressed. This is the case with my 2007 HHR but if you have to pull or bypass #8 fuse in your vehicle, check this out before you cut into the brake light switch wiring. Might save you quite a bit of time, some money and grief--another of life's lessons!