A CANBUS where no messages are transmitted is running at 2.5 Volts constantly for both CAN high and CAN low (blue and red lines).
CANBUS system without a controller connected:
Total message count does not count up, and network status is inactive.
When messages are transmitted, CAN high will rise up to 3.5 Volts, and CAN low will decrease down to 1.5 Volts. Voltage can change up to 256,000 times per second, resulting in a voltage change for only 4 µs (4 millionths of a second).
CANBUS system with voltage changes:
Red line shows CAN high, and blue line shows CAN low.