CAN

📖 YOUCANIC Automotive Glossary

CAN (Controller Area Network) is the primary digital communication protocol connecting vehicle modules and diagnostic scan tools. Mandatory on all US vehicles since 2008, CAN Bus uses a twisted pair of wires (CAN High and CAN Low) carrying differential voltage signals — CAN High swings to ~3.5V and CAN Low drops to ~1.5V during transmission, resting at ~2.5V. This provides excellent noise immunity. Data transmits as digital frames containing an identifier, data bytes, and error-checking information.

Modern vehicles have multiple CAN networks: high-speed (500 kbps) for powertrain/chassis and low-speed (125 kbps) for body electronics, connected through a gateway module. Each CAN Bus has a 120-ohm termination resistor at each end. DIYers can verify network integrity by measuring between CAN High (pin 6) and CAN Low (pin 14) at the OBD2 port with ignition off — should read ~60 ohms (two 120-ohm resistors in parallel). CAN faults cause widespread symptoms as multiple modules lose communication, triggering multiple U-codes.