Troubleshooting J1939 Multiplexing The J1939 is a twisted pair of wires in the multiplexing system between modules that communicates using inputs and outputs. Multiplexing can be compared to broadband cable supplying internet access, cable TV and telephone. It sends multiple electronic messages using the same signal path simultaneously with other signals. The J1939 also known… Continue reading C2 School Bus J1939 Wiring