COVER ASSEM. 4L9893 - Caterpillar

Overview
These engines are equipped with an electronic control system. The system consists of a computer, sensors, and software. The system performs these functions:
Control of the engine
Control of the Selective Catalyst Reduction (SCR) system
Applications control system interface
Fault detection and reportingElectronic Control System
The Electronic Control Module (ECM) is a computer that controls the operation of the engine.The ECM contains a flash file. The flash file is the software for the ECM. The flash file contains the operating maps. The operating maps define the following characteristics of the engine:
Horsepower
Torque curves
Engine speed (rpm)Refer to Troubleshooting, "System Overview" for additional information on the electronic control system.Application Interface
The ECM interfaces with the machine via software and an electrical connector on the ECM. The software can be configured.The application control system provides inputs to the electrical connector on the ECM to indicate the status of switches. Correctly configure the ECM to interpret the inputs.The ECM provides outputs for the application control system via the electrical connector to control lamps, solenoids, and other devices. Correctly configure the ECM in order for the outputs to match the configuration of the application control system.Clean Emissions Module (CEM)
The CEM contains these components:Selective Catalyst Reduction (SCR) System - The SCR system is used to reduce nitrous oxide (NOx) emissions from the engine.Software - The software controls the amount of Diesel Exhaust Fluid (DEF) being injected into the exhaust stream.Fault Detection and Reporting
The ECM monitors inputs from the sensors and inputs from the applications control system. Software in the ECM interprets the inputs. The software determines if the inputs are operating correctly. A diagnostic trouble code is activated when the software detects a problem with an input.The ECM broadcasts the codes on two data links. The data links are the Cat Data Link (CDL) and J1939. Cat® Electronic Technician (ET) must communicate on both data links to service the engine. If a problem is suspected with one of the data links, refer to Troubleshooting, "Data Link - Test".The codes can be displayed on Cat ET and optional operator interfaces. Refer to Troubleshooting, "Diagnostic Trouble Codes" for additional information on diagnostic trouble codes and a complete list of codes.Troubleshooting
As a reference, simplified schematics for each of the engine subsystems are included with each of the circuit tests that are in this manual. For an accurate representation of the entire electrical schematic that is for your application, refer to the Electrical System Schematic.During troubleshooting, inspect all harness connections before any component is replaced. If these connections are not clean and tight, continuous electrical problems or intermittent electrical problems can result. Check that the wires are pushed into the connectors completely. Make sure that the connections are tight before other tests are made.Failure of an electrical component may cause the failure of other components. Always attempt to correct the cause of an electrical failure before you replace a component. If wire insulation is punctured, repair the damage. Seal the damaged wires with 8T-0065 Silicone Sealant. Cover the sealant with two layers of