Circuit Description
Inputs, such as throttle pedals, switches, and sensors, can be communicated to the ECM over the J1939 datalink. Messages sent from the vehicle electronic control units (VECUs) are
received by the ECM and used for controlling the engine. Both the ECM and VECU must be
properly configured so that each device’s information is transmitted by the VECU and received
by the ECM.

Component Location
The ECM is located on the intake side of the engine, about mid-engine. The J1939 datalink
wiring and VECU(s) vary by OEM options.

Shop Talk
This fault occurs when the ECM is set up to receive information from several multiplexed
switches from VECU(s) and only receives some of the switches. It indicates the ECM is set up
to receive too many switches or the VECU(s) is set up to transmit too few switches.