Group 28 Engine Control Module (ECM) Diagnostic Trouble Codes (DTCs) System Electronic Control Unit (ECU) Overview The engine control module (ECM) monitors and models (using physical principles) engine parameters to monitor the engine system’s performance in real time. This is performed to aid the ECM with its self diagnostic capabilities. Many sensors are used for input to the emission control system. These ECUs all communicate with the ECM via data links. The VECU communicates across the SAE J1939 (CAN1) data link while the others use the SAE J1939-7 (CAN2) data link.
The OBD systems use SAE J1939 data link protocol for communication with scan tools but, MACK trucks still are capable of communicating via the SAE J1587 data link for diagnostics. The use of a scan tool is necessary to perform diagnostic work as well as clearing of any diagnostic trouble codes (DTCs). DTC(s) can no longer be cleared using the vehicles instrument cluster digital display and stalk switch control.
The system contains the following “emission critical” ECUs that are monitored; Engine Control Module (ECM) Vehicle Electronic Control Unit (VECU) Aftertreatment Control Module (ACM) Aftertreatment Nitrogen Oxides (NOx) Sensors Engine Variable Geometry Turbocharger (VGT) Smart Remote Actuator (SRA) There are other ECUs such as the Instrument Control Module (ICM), Transmission Control Module (TCM) and Anti-lock Brake System (ABS) Module that provide data to the emission control system or the diagnostic system but are not “emission critical”. Malfunction Indicator Lamp (MIL), Description and Location A MIL located in the instrument cluster.
This amber colored lamp is used to inform the driver that a “emission critical” malfunction signal has occurred. W2036007 SAE J1939 Data Link Communication The electronic control units (ECUs) that communicate on the SAE J1939 data link, communicate according to the SAE J1587 standard. The diagnostic trouble codes (DTCs) set by the ECUs contain information that is described by the following abbreviations. SA Source Address: Identification of a control module. SPN Suspect Parameter Number: Identification of a parameter (value). FMI Failure Mode Identifier: Identification of fault types. 4