80-J4866-2 Rev. G
MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION
11-3
Vehicle Data Bus Connections
Vehicle Data Source Selection
Vehicle Data Source Selection
When making data source connections, there are two possible data buses available: the
J1708 /J1587 low-speed data bus and the J1939 high-speed data bus. The truck year, make,
and model, as well as the Omnitracs applications used determine which data bus to use.
If you do not know which data source to use, contact your Omnitracs representative for
assistance.
Guidelines for Connecting to the J1939 Data Bus
• Choose Option 1, Option 2, or Option 3 depending on which accessory cable is used.
• DO NOT extend factory wires.
• Maximum stub length is 10 feet.
• Minimum stub spacing is 4 inches.
• Never have more than one ECM device on the same stub.
Termination Resistors at Ends of the Main Backbone
Each 120 Ohms 5 % 1/4W
CAN_H
CAN_L
To ECM
08AAA_053Dem
Stub
Stub
Stub
4 in Min
4 in Min
10 ft. Max
ECM
Device
Never have more than
one ECM on the same stub
Reads 60 ohms when measured in parallel from CAN_HIGH to CAN_LOW
ECM
Device
