309-00121-0 Nissan OIL SEAL, 20 - 42 - 8

Electronic Controls
The 3176B Marine Engines electronic system consists of two main components: the Electronics [Electronic Control Module (ECM) and Sensors] and the Personality Module. The ECM is the computer which controls the 3176B engine. The Personality Module contains the software which controls how the ECM behaves (the personality module stores the operating maps that define horsepower, torque curves, rpm, etc). The two must be used together: neither can do anything by itself.The ECM determines a "desired rpm" based on the throttle signal and certain diagnostic codes. The ECM then maintains the desired engine rpm by sensing actual engine rpm and deciding how much fuel to inject in order to achieve the desired rpm.Fuel Injection
The ECM controls the amount of fuel injected by varying signals to the injectors. The injectors will inject fuel ONLY if the injector solenoid is energized. The ECM sends a 100 volt signal to the solenoid to energize it. By controlling the timing and duration of the 100 volt signal, the ECM can control injection timing and the amount of fuel injected.The ECM sets certain limits on the amount of fuel that can be injected. "FRC Fuel Pos" is a limit based on boost pressure to control the fuel to air ratio, for emissions control purposes. When the ECM senses a higher boost pressure (more air into cylinder), it increases the "FRC Fuel Pos" limit (allows more fuel into cylinder). "Rated Fuel Pos" is a limit based on the horsepower rating of the engine. It is similar to the rack stops and torque spring on a mechanically governed engine. It provides horsepower and torque curves for specific engine family and rating. All of these limits are programmed at the factory into the Personality Module and are not programmable in the field.Injection timing depends on engine rpm, load and other operating factors. The ECM knows where top center on cylinder number one is from the signal provided by the engine Speed/Timing Sensor. It decides when injection should occur relative to top center and provides the signal to the injector at the desired time.Caterpillar Engine Monitoring
Caterpillar provides a factory installed Engine Monitoring system. The Caterpillar Engine Monitoring system monitors engine oil pressure, coolant temperature, intake manifold air temperature, and coolant level. The oil pressure, intake manifold air temperature, and coolant temperature sensors are standard on all engines. The Vessel OEM is responsible for providing the coolant level sensor and the associated harness. The coolant level sensor is the only individually selectable component of Caterpillar Engine Monitoring. It is ENABLED or DISABLED through a Customer Programmable Parameter.Caterpillar Engine Monitoring can be programmed to four different modes; OFF, , DERATE and SHUTDOWN with the additional option of enabling or disabling the Coolant Level Sensor. The Coolant Temperature, Oil Pressure, and Coolant Level (if enabled) Sensors will operate in the Engine Monitoring Mode selected. For example, if DERATE mode were selected, the engine will derate engine HP if the Coolant Temperature, Oil Pressure, or Coolant Level (if enabled) Sensors detect conditions exceeding acceptable limits. The Oil Pressure Sensor can not be selected for , while the Coolant Temperature Sensor operates in a different mode such as DERATE.An excessive Intake Manifold Air Temperature will not derate the engine. If the Engine Monitoring Mode is programmed to DERATE, and a 105-11 Very High Intake Manifold Air Temperature Diagnostic Code is Active, the engine will Warn, but will not Derate the engine.Caterpillar Engine Monitoring Off
If Caterpillar Engine Monitoring is programmed to OFF, the control system disables those diagnostics associated with Caterpillar Engine Monitoring as shown in the following table.Diagnostic Codes Enabled for Caterpillar Engine Monitoring
The engine will still use the Coolant Temperature Sensor signal for Cold Mode operation, and the diagnostics available for flagging incorrect sensor operation (Coolant Temp Sensor Open/Short Circuit). The Intake Manifold Air Temperature Sensor signal will also still be used for timing advance. The 105-00 High Intake Manifold Air Temperature Warning and 105-11 Very High Intake Manifold Air Temperature will be logged regardless of the engine monitoring mode. The Oil Pressure Sensor signal will be ignored. Because the Oil Pressure Sensor and Coolant Level Sensor harnesses are still present on the engine, the harness could cause a problem in the event it had a short circuit in the supply wire to ground. Therefore, these items should not be excluded from diagnostic procedures.Caterpillar Engine Monitoring Warning Mode Operation
If the system is programmed to the ECM will indicate the diagnostic codes, listed in the following tables, are active through the Check Engine/Diagnostic Lamp, and will also turn the Warning Lamp on solid when the necessary conditions exist. No further action occurs if the ECM is programmed to .Caterpillar Engine Monitoring Derate Mode Operation
If the system is programmed to DERATE the ECM will indicate the diagnostic codes listed in the following table are active through the Check Engine/Diagnostic Lamp. Conditions causing Diagnostic Codes 100-01 Low Oil Pressure Warning, 111-01 Low Coolant Level Warning, 105-00 High Intake Manifold Air Temperature Warning and 105-11 Very High Intake Manifold Air Temperature Warning will cause the Warning Lamp to come on solid. Conditions causing Diagnostic Codes 110-00 High Coolant Temperature Warning, 110-11 Very High Coolant Temperature Warning, 100-11 Very Low Oil Pressure Warning and 111-11 Very Low Coolant Level Warning will cause the Warning Lamp to begin to flash. The Warning Lamp flashes whenever the engine is derated. During DERATE mode the Warning Lamp will begin to Pulse (the Diagnostic/Check Engine Lamp will flash indicating the presence of an Active diagnostic code), and the available engine power will be limited (if due to Very Low Oil Pressure, engine speed is also limited).There are tables and graphs shown on the following pages detailing Caterpillar Engine Monitoring Operation with respect to each Diagnostic Code and sensor of the system.Programmed to
Programmed to DERATE
Programmed to SHUTDOWN
Caterpillar Coolant Temperature Engine Monitoring Operation
The following graph indicates operation of Caterpillar Coolant Temperature Engine Monitoring. This graph indicates a Coolant Temperature of 103°C (217°F) triggers ECM action. The three tables on the previous page