How to output 5V from PWM pins of Teensy 2++

According to the link given, 0 is low and 256 is constant high. If those values don't work, I would just try to >>> digitalWrite(<pin>, HIGH); <<<
Have you tried measuring with a DVM ? or remembering to connect GND on the scope to GND on your project ?
The PWM pin I used (15) of Teensy2++ will output a voltage signal at frequency of 3921.57 Hz, which is hard to use digital voltage meter to measure, but I tried it shows 0V, clearly not 5V.

I think connecting ground is not a problem, because I measure the 5V pin using oscilloscope and it shows right.
Problems solved. I didn't disconnect the teensy from other circuits and measured wrong. When I disconnect with other circuits, it is 5 V as high voltage.