A/T Neutral Switch

[barryware]

2007 yaris hatch / AT

When I bought the car (new), I immediately installed a Rostra cruise control. This is the same unit the dealer would install.

Lately, when the cruise control is engaged it will shut off as if you were to tap the brakes. More often than not, it shuts off when I hit a bump.

There is only one wire that goes through the firewall and connects to a wire harness plugged into the transmission. I believe this wire connects to the neutral switch wire.

My question: When the car is placed in neutral, does the neutral signal wire get grounded, or does it get a voltage signal?

I'm thinking that over the years / miles, the Rostra wire may have gotten some insulation rubbed off and now it is rattling around and when circumstances are right, the wire may go to ground and disengage the cruise.

I haven't really checked it out just yet because the weather has been so bad. Even in my garage, the floor is always wet, it is cold, etc.