Circuit DescriptionThe fan clutch solenoid is a device used by the ECM to control the engine fan by sending asignal to open or close the fan clutch solenoid. Component LocationRefer to an original equipment manufacturer’s (OEM) diagram for the location of the fan clutch solenoid. Shop Talk1) Fan clutch solenoid could be malfunctioning due to a failed engine harness or a badground on the fan clutch connector.2) Use your diagnostic tool to make sure that on/off fan feature is enabled and the right ON voltage is chosen. Cummins ISB CM550 (1990-94) Fault Code: 243 PID: 121 SPN: 513 FMI: 4...

Circuit DescriptionNormally, switches, accelerators, and other components are connected to the engine controlmodule (ECM) directly through individual wires. Multiplexing allows those same components tobe hard wired to an original equipment manufacturer (OEM) vehicle electronic control unit(VECU) or transmission electronic control unit (ECU) in the cab. Component values and statesfrom components such as sensors, accelerators, and switches can then be transmitted fromthe OEM VECU to the Cummins ECM over the data link. Messages sent from OEM VECUs or transmission ECUs are received by the Cummins ECMand used for controlling the engine. The Cummins Inc. ECM and OEM VECU(s) must beconfigured properly...

Circuit DescriptionThe fuel temperature sensor is located in the fuel pump. Fuel temperature information ispassed to the engine control module (ECM) through the controller area network datalink. Component LocationThe fuel temperature sensor is located in the fuel pump. Shop TalkThis fault code is typically set when the fuel pump controller communicates to the ECM that the fuel temperature measured in the fuel inlet to the pump (temperature sensor) exceeds the allowable threshold value (93°C [199°F]). This signal does not set a final temperature defect in the controller and, in most cases, identifies a fuel overheat condition on the engine/vehicle. Cummins...

Circuit DescriptionThis fault indicates a final defect of the temperature sensor. The sensor’s reading indicates an unrealistic value, or the temperature is outside of the signal range check thresholds, -45°C [-49°F] to 130°C [266°F]. Component LocationThe circuit for this fault code is contained within the Bosch® fuel pump control module. Shop TalkThe table below relates which actions are taken by the engine control module (ECM) or fuelpump control module when Fault Code 264 becomes active. When a defect occurs within the controller temperature sensing circuit, the controller defaults to a temperature value of 75°C [167°F]. If this is the temperature’s...

Circuit DescriptionThe electronic control module (ECM) enables the lift pump by sending a signal directly to the lift pump. The ECM fast-duty cycles the lift pump ON and OFF during cranking, and it enables the pump once the engine has started. Component LocationThe lift pump is mounted to the engine block on the intake side, toward the rear of the engine. Shop Talk1) The lift pump is turned ON for approximately 5 seconds when the keyswitch is first turned ON. With the hood raised, it is possible to hear the lift pump running when the keyswitch is turned ON.2) Loose...