Electronic Controls
Electronic Control Module
The ECM consists of three main components, the control computer (hardware), the flash file (software) and the configuration file. The control computer consists of a microprocessor and electronic circuitry. The flash file is the software for the control computer which contains the operating maps that define power and torque curves. The configuration file contains the adjustable settings for the engine monitoring system. The configuration file also allows the customer to enable optional equipment. The customer can fine tune the engine by modifying the settings in the configuration file. The engine is shipped from the factory with default values for these settings. If the settings have been modified, there will be no record at the factory of the changes. These settings can be downloaded into a laptop computer and saved to a file. The customer can then use the file in order to ease the future replacement of the ECM.
Engine Governor
The engine ECM governs engine speed. Desired engine rpm is determined by the throttle position sensor signal and certain sensor readings. Diagnostic codes may be accompanied by a reduction in the available power from the engine. The reduction in power is typically called an engine derate. Actual engine rpm is measured by the engine speed/timing signal.
Fuel Injection
The engine ECM controls the timing and the duration of the fuel that is injected. The engine ECM varies the signals to the unit injectors. Fuel is injected only while an injector solenoid is energized by a 105 volt signal from the engine ECM. The timing of the injection signal determines the engine timing. The length of the injection signal determines engine speed. By controlling the timing and duration of the 105 volt signal, the ECM controls the engine speed.
Injection timing depends on the following conditions: desired engine rpm and load. The ECM detects the top center position of each piston. The ECM sends an injection signal at the desired time.
Cold Mode Operation
During a cold start or extended periods at low idle, the engine ECM will automatically turn off one unit injector at a time in order to determine if the cylinder is firing. Cold mode operation automatically stops fuel injection to cylinders that are not firing. Cold mode operation has the following benefits: increased startability, reduced warm up period and reduced white smoke. The cold cylinder cutout strategy is activated whenever the engine coolant temperature falls below 63 °C (145 °F) and the following conditions are met:
- An engine without the ether option has been running for ten seconds.
- Ether injection has been completed for three seconds.
- The engine has been idling for ten minutes.
The engine will exit cold mode for ten minutes under the following conditions:
- Engine speed drops 50 rpm below low idle.
- The throttle switch position is changed.
The engine will exit cold mode under the following conditions:
- The coolant temperature rises above 70 °C (158 °F).
- The Cylinder Cutout Test on Caterpillar Electronic Technician (ET) is activated.
FRC Limit
The flash file inside the engine ECM sets certain limits on the amount of fuel that can be injected. The FRC limit is a limit that is based on the boost pressure. The boost pressure is calculated as the difference in pressure between atmospheric pressure and turbocharger outlet pressure. The FRC limit is used to control the air/fuel ratio for control of emissions. When the engine ECM senses a higher boost pressure, the engine ECM increases the FRC limit. A higher boost pressure indicates that there is more air in the cylinder. When the engine ECM increases the FRC limit, the engine ECM allows more fuel into the cylinder.
Rated Fuel Position
The rated fuel position is a limit that is based on the power rating of the engine. The rated fuel position is similar to the rack stops and the torque spring on a mechanically governed engine. The rated fuel position determines maximum power and torque values for a specific engine family and for a specific rating. The rated fuel position is programmed into the flash file at the factory.
Electronic Governor
 | |
| Illustration 1 | g00752115 |
Electronic Governor | |
Engine Wiring Diagram
 | |
| Illustration 2 | g01262074 |
Typical | |
Typical Location of the Engine Sensors on 3508B and on 3512B
 | |
| Illustration 3 | g01262225 |
Left Side View (1) Unfiltered fuel pressure sensor (2) Filtered fuel pressure sensor (3) Aftercooler temperature sensor (4) Connector for the left air shutoff solenoid (5) Connector for the left turbocharger inlet pressure sensor (6) Left exhaust temperature sensor (7) Service tool connector (8) Secondary engine speed/timing sensor (9) Machine interface connector (10) Primary engine speed/timing sensor (11) Unfiltered engine oil pressure sensor (12) Filtered engine oil pressure sensor | |
Typical Location of the Engine Sensors on 3508B and on 3512B
 | |
| Illustration 4 | g01262226 |
Right Side View (13) Right exhaust temperature sensor (14) Connector for the right turbocharger inlet pressure (15) Connector for the right air shutoff solenoid (16) Timing calibration sensor (17) Crankcase pressure sensor | |
Typical Location of the Engine Sensors on 3508B and on 3512B
 | |
| Illustration 5 | g01262227 |
Front View (18) Atmospheric pressure sensor (19) Coolant temperature sensor (20) Turbocharger compressor outlet pressure sensor (21) Connector for the optional engine oil temperature sensor (22) J1 ECM connector (23) Engine ECM (24) J2 ECM connector | |
Location of the Engine Sensors 3516B
 | |
| Illustration 6 | g01262231 |
Left Side View (25) Unfiltered fuel pressure sensor (26) Filtered fuel pressure sensor (27) Aftercooler temperature sensor (28) Connector for the left air shutoff solenoid (29) Left exhaust temperature sensor (30) Connector for the left turbocharger inlet pressure sensor (31) Service tool connector (32) Secondary engine speed/timing sensor (33) Machine interface connector (34) Primary engine speed/timing sensor (35) Unfiltered engine oil pressure sensor (36) Filtered engine oil pressure sensor | |
Location of the Engine Sensors 3516B
 | |
| Illustration 7 | g01262228 |
Right Side View (37) Connector for the right turbocharger inlet pressure (38) Right exhaust temperature sensor (39) Connector for the right air shutoff solenoid (40) Timing calibration sensor (41) Crankcase pressure sensor | |
Location of the Engine Sensors 3516B
 | |
| Illustration 8 | g01262234 |
Front View (42) Atmospheric pressure sensor (43) Coolant temperature sensor (44) Turbocharger compressor outlet pressure sensor (45) Connector for the optional engine oil temperature sensor (46) J1 ECM connector (47) Engine ECM (48) J2 ECM connector | |