Usage:
System Operation
The 3512 Industrial Engine is an electronically controlled engine equipped with an Electronic Control Module (ECM) to control fuel rate instead of using flyweights and linkages found in mechanically governed engines. The electronic control system also replaces the mechanical fuel ratio control (FRC), the torque control group, and various adjustment screws.
The ECM uses several sensor input signals to calculate desired rack position and varies the voltage to the Mechanical Unit Injection (MUI) Interface Module. The MUI Interface Module drives the Rack Actuator which is connected to the rack by an external linkage. The Rack Position Sensor indicates when desired rack position is reached.
Electronic Controls
The electronic control system consists of three main components: the ECM, the Personality Module, and the MUI Interface Module. The ECM is the computer hardware which controls the engine and the Personality module is the software which controls how the computer behaves. The MUI Interface Module provides signal conditioning that allows the ECM to position the rack actuator.
Rack Controls
The ECM determines the desired engine rpm based on throttle inputs and load. The ECM attempts to maintain the desired engine rpm by sensing actual engine rpm with the Engine Speed Sensor and controlling the rack.
To move the rack, the ECM adjusts the signal voltage to the MUI Interface Module, which adjusts current to the Rack Actuator to increase or decrease rack. The ECM increases or decreases the signal voltage to the MUI Interface Module until the Rack Position Sensor indicates that the desired rack position has been reached.
The ECM sets certain limits on the amount of fuel that can be injected. FRC Rack is a rack limit used to reduce smoke during acceleration and operates in a manner similar to the FARC on a mechanically governed engine. When the ECM senses a higher inlet manifold (Boost) pressure (more available air for combustion), the FRC Rack limit is increased to allow more fuel. Rated Rack is a limit based on the power rating of the engine. It is similar to the rack stops and the torque spring on a mechanically governed engine. Rated Rack determines maximum power and torque values for a specific engine family and rating. FRC Rack and Rated Rack are programmed by the factory into the Personality Module.
Figure 1.1 - Electronic Governor Block Diagram
Programmable Parameters
Certain parameters that effect engine operation may be changed with an electronic service tool. These parameters are stored in the ECM and are either System Configuration Parameters or Customer Parameters. System Configuration Parameters are parameters that affect power ratings or emissions. Customer Parameters affect settings such as low and high idle rpm.
Passwords
System Configuration Parameters are protected from unauthorized changes by Factory Passwords. Customer Parameters are protected by Customer Passwords that are programmed by the customer.
Self-Diagnostics
The ECM has some ability to diagnose itself. When a problem is detected, a diagnostic code is generated and the diagnostic code is indicated on the Diagnostic Lamp as a series of flashes. In most cases, the diagnostic code is also stored in permanent ECM memory.
A diagnostic codes that represent a currently existing problem is called ACTIVE. ACTIVE codes should always be serviced first.
Diagnostic codes that are stored in memory are called LOGGED. Since the problem may have been temporary, or may have been repaired since the time it was logged, Logged diagnostic codes do not necessarily mean something needs to be repaired. Instead, they are meant to be an indicator of probable causes for intermittent problems. In addition, some logged diagnostic codes record EVENTS rather than failures.
Diagnostic codes not requiring factory passwords to clear are automatically erased after 100 ECM operating hours. Refer to Section 4: Troubleshooting Without A Diagnostic Code for details.
System Alarm Outputs
The ECM provides outputs to drive three different warning lamps to alert the operator of certain operating conditions. These lamp outputs are:
- * Low Oil Pressure
- * High Coolant Temperature
- * Diagnostic
- * High Coolant Temperature
The Diagnostic Lamp displays diagnostic conditions detected by the ECM using flash codes. Refer to P-505: Alarm Lamps for additional information.
Figure 1.2 - System Alarm Outputs
System Component Diagram
Figure 1.3 - System Component Diagram
Engine Sensor And Connector Locations
Figure 1.4 - Engine Sensor And Connector Locations
Engine Sensor And Connector Locations
Figure 1.5 - Engine Sensor And Connector Locations
Connector Pin Descriptions
Electrical Connectors And Functions
Electronic Service Tools
Caterpillar Electronic Service Tools are designed to help the service technician obtain and analyze data and diagnose existing and potential problems within the system. Their use is required to perform calibrations and to read or change programmable parameters.
The electronic service tools for use with the engine are the Electronic Technician (ET) and Electronic Control Analyzer Programmer (ECAP). They are able to communicate with the ECM, read diagnostic codes (CID-FMI), read and monitor various sensor output signals (such as engine speed and boost pressure), electronically calibrate certain sensors, and read or change parameters.
A digital multimeter suitable for making voltage, resistance, frequency, and duty cycle measurements There are also several adapter cables, probes, etc, used to allow the service technician to perform the required measurements needed for diagnosis. These tools are listed in the following tables and diagrams, along with their associated part numbers.
Jumper and extension wires will be needed to check continuity of some wiring harness circuits. Jumper wires are used to short (connect) two adjacent pins or sockets together in a connector.
Additional Service Tools
The following list contains service tools that are helpful to service the engine.
Electronic Technician (ET)
Caterpillar Electronic Technician (ET) is a service tool designed to run on a personal computer (laptop). The software allows the laptop to display the status of a group of parameters (temperatures, pressures, etc) view and clear active and logged diagnostic codes, display the current ECM configuration, perform diagnostic tests and calibrations.
Figure 1.6 - Laptop Computer Based ET
Connecting ET And The Communication Adapter Tool
The Communication Adapter Tool operates on 24 VDC supplied by the battery. Use the following procedure to connect ET and the Communication Adapter Tool to the engine.
1. Turn the Engine Control Switch to the OFF position. If the Engine Control Switch is not placed in the OFF position, the engine may start and run.
2. Connect the 139-4166 cable between the Service Tool Connector (J13, 9-Pin connector) and the Communication Adapter CONTROL connector.
3. Connect the 7X1425 cable between the laptop RS232 serial port and the Communication Adapter SERVICE TOOL connector.
4. Turn the Engine Control Switch to the ON position, engine OFF to begin testing. The ET and Communication Adapter Tool will operate with the engine running or with the engine off (Engine Control Switch ON). If ET and the Communication Adapter Tool do not communicate with the ECM, refer to P-310: Electronic Service Tool Will Not Communicate With The ECM.
Electronic Control Analyzer Programmer (ECAP)
Electronic Control Analyzer Programmer (ECAP) requires a small plug-in module, called a Service Program Module (SPM NEXG4516), to adapt the basic ECAP to your application. The ECAP can display diagnostic codes, measure pulse width modulated (PWM) signals (with a PWM adapter), and program parameters, The ECAP can also program certain System Configuration Parameters and calibrate certain sensors. The ECAP can display the status of up to eight sensors or switches at one time, print parameters with the 9U7554 Rechargeable Portable Printer, and can be used with additional Service Program Modules for other applications.
Figure 1.7 - 8T8697 ECAP Service Tool
Connecting ECAP To The Engine ECM
The Electronic Control Analyzer Programmer (ECAP) and the Communication Adapter Tool operate on 24 VDC supplied by the equipment's batteries. Use the following procedures to connect the ECAP to the Service Tool data link Connector.
1. Turn the Engine Control Switch to the OFF position.
2. Connect the 8T5275 or 139-4166 cable between the Service Tool Connector (J13, 9-Pin connector) and the ECAP Port 1 connector.
3. Turn the Engine Control Switch to the ON position, engine OFF to begin testing. The ECAP will operate with the engine running or with the engine off (Engine Control Switch ON). If ECAP does not communicate with the ECM, refer to P-310: Electronic Service Tool Will Not Communicate With The ECM.
NOTE: The Electronic Service Tool may restart during engine cranking due to a voltage dip on the battery line.
Service Tools Diagram
Figure 1.8 - Service Tools