Electrical 579 Family
Peterbilt Motors Company 7-26
J1939
Warning! The J1939 databus is the communication link between the engine and the Anti-Lock Braking System
(ABS). Only J1939 compatible devices should be added to the databus. Some J1939 compatible aftermarket devices may
disrupt the ability of the databus to communicate. If the databus is disrupted by an aftermarket device, it must be removed
from the databus.
Guidelines - J1939 Circuit Requirements
Circuits added must be a twisted pair consisting of a minimum of 1 twist per inch.
Individual breakout length of circuits added cannot exceed 118 inches.
Do not splice into existing J1939 circuits. Use the connection points provided.
J1939 circuits are for data transmission only and are not to be used for power or ground circuits.
Any modifications must conform to SAE J1939.
J1939 Access
All Peterbilt vehicles include J1939 circuitry. The J1939 circuit can be accessed in two locations. The first access is lo-
cated inside the dash near the diagnostic connector. The second access is at the driver side toward the rear of the
engine.
1. Dash Access - Connector located in dash behind key switch panel approximately 1 foot down the harness
FIGURE 7-24. Dash Access
