The CAN (Control Area Network) is a serial data communication system for real time application. It is a vehicle multiplex communication system which has a high communication speed (500 kbps) and the ability to detect malfunctions.
If some ECUs and sensors are not displayed on the "Communication Bus Check" screen of the intelligent tester and some ECUs and sensors repeatedly appear and disappear from the screen when the CAN main bus lines are normal (there is no open, short, short to B+, or short to GND in the main bus lines), there may be an open circuit in either of the CAN branch lines.
A short to GND is suspected in the CAN bus line when the resistance between terminals 4 (CG) and 6 (CANH), or terminals 4 (CG) and 14 (CANL) of the DLC3 is below 1 kΩ.
A short to B+ is suspected in the CAN bus line when the resistance between terminals 6 (CANH) and 16 (BAT), or terminals 14 (CANL) and 16 (BAT) of the DLC3 is below 1 MΩ.
There may be an open circuit in the CAN main bus line and/or the DLC3 branch line when the resistance between terminals 6 (CANH) and 14 (CANL) of the DLC3 is 69 Ω or more.