Circuit DescriptionInputs, 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) arereceived by the ECM and used for controlling the engine. Both the ECM and VECU must beproperly configured so that each device’s information is transmitted by the VECU and receivedby the ECM. Component LocationThe ECM is located on the intake side of the engine, about mid-engine. The J1939 datalinkwiring and VECU(s) vary by OEM options. Shop TalkThis fault occurs when the ECM is set up to receive information about a multiplexed devicefrom...

Circuit DescriptionInputs, 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) arereceived by the ECM and used for controlling the engine. Both the ECM and VECU must beproperly configured so that each device’s information is transmitted by the VECU and receivedby the ECM. Component LocationThe ECM is located on the intake side of the engine, about mid-engine. The J1939 datalinkwiring and VECU(s) vary by OEM options. Shop TalkThis fault occurs when the ECM is set up to receive information from several multiplexedswitches from...

Circuit DescriptionThe OEM sensor signal is used by the electronic control module (ECM) to monitor the OEMpressure. The OEM pressure is used by the ECM in one of two ways:1. The ECM can shutdown the engine based on an OEM pressure input value exceeding or falling below acustomer-specified value.2. The ECM can control a device (dual-output driver A and driver B)based on the value of the OEM pressure.A sensor that has failed high can be caused by anopen circuit in the signal or return wire, voltage shorts in the signal or return wire, or a faultysensor. Component LocationThe location varies...

Circuit DescriptionThe OEM sensor signal is used by the electronic control module (ECM) to monitor the OEMpressure. The OEM pressure is used by the ECM in one of two ways:1. The ECM can shutdown the engine based on an OEM pressure input value exceeding or falling below acustomer-specified value.2. The ECM can control a device (dual-output driver A and driver B)based on the value of the OEM pressure.A sensor that has failed low can be caused by shorts to ground on the signal wire or an internally grounded (faulty) sensor. Component LocationThe location varies with the OEM. Refer to the...

Circuit DescriptionThe auxiliary speed input is a frequency signal from an auxiliary speed or pressure pickup. It is sent to the electronic control module (ECM) and is used to control the engine speed. Auxiliary reference speed is based on the throttle position. Component LocationThe auxiliary speed or pressure pickup device location is dependent on the original equipment manufacturer’s (OEM) application. Refer to OEM troubleshooting and repair manual forcomponent location. Shop TalkThe auxiliary speed governor controls engine speed based on a measured auxiliary speed orpressure. The auxiliary speed governor feature must be enabled in the calibration and setproperly for speed or...