3176C and 3196 Engines for Caterpillar Built Machines Caterpillar

Illustration 1	g01298159
Top view (1) Coolant temperature sensor (2) Inlet air temperature sensor (3) Boost pressure sensor (4) Atmospheric pressure sensor

Illustration 2	g01298228
Front view and left side view (5) Fuel temperature sensor (6) Crankshaft position sensor (7) Camshaft position sensor (8) Oil pressure sensor (9) Engine control module (ECM)

The electronic control system is integrally designed into the engine's fuel system and the engine's air inlet and exhaust system in order to electronically control the fuel delivery and the injection timing. The electronic control system provides increased timing control and fuel air ratio control in comparison to conventional mechanical engines. Injection timing is achieved by precise control of injector firing time, and engine rpm is controlled by adjusting the firing duration. The Engine Control Module (ECM) energizes the solenoid in the unit injector in order to start the injection of fuel. Also, the ECM de-energizes the unit injector solenoids in order to stop injection of fuel. Refer to the Systems Operation, "Fuel System" topic for a complete explanation of the fuel injection process.

The engine uses the following types of electronic components:

• Inputs

• Controls

• Outputs

An input component is one that sends an electrical signal to the ECM. The signal that is sent varies in one of the following ways:

• Voltage

• Frequency

• Pulse width

The variation of the signal is in response to a change in some specific system of the vehicle. The engine control module sees the input sensor signal as information about the condition, environment, or operation of the vehicle.

A control component (ECM) receives the input signals. Electronic circuits inside the control component evaluate the signals from the input components. These electronic circuits also supply electrical energy to the output components of the system. The electrical energy that is supplied to the output components is based on predetermined combinations of input signal values.

An output component is one that is operated by a control module. The output component receives electrical energy from the control component. The output component uses that electrical energy in one of two ways. The output component can use that electrical energy in order to perform work. The output component can use that electrical energy in order to provide information.

1. As an example, a moving solenoid plunger will perform work. By performing work, the component has functioned in order to regulate the vehicle.

2. As an example, a dash panel light or an alarm will provide information to the operator of the vehicle.

These electronic components provide the ability to electronically control the engine operation. Engines with electronic controls offer the following advantages:

• Improved performance

• Improved fuel consumption

• Reduced emissions levels