I went wanted to have my D3 bypassed, so I took it to a local technician and gave him the bypass instructions. He said that the mute wire was not installed, so he could not do the regular bypass procedure. Instead, he put a toggle switch in my glove compartment. It works fine when the car is parked or moving slowly, but whenever the car reaches 10-15 mph the bypass stops working. Is this due to faulty wiring or is the D3 using its own speed detector to disable the bypass?

No, you don't need a switch. He didn't follow the directions, so the bypass doesn't work.

It has to be done EXACTLY as shown in one of the 3 stickied topics explaining the procedure, or IT WILL NOT WORK.

The guy is an idiot. That's how you bypass many units but not the new pioneer navigations. I hope you didn't pay him.