3516B and 3516B HD Engines and 994D, 994F, and 994H Wheel Loaders Caterpillar

The electronic control module (ECM) is the computer which controls the engine. The personality module is the software which controls the behavior of the ECM.

Illustration 1	g00284603
Fuel cooled ECM. Typical example (1) Fuel outlet (2) ECM (3) Fuel inlet

Illustration 2	g01135565
Air cooled ECM.

The ECM (2) is cooled by fuel as the fuel circulates through a manifold that is inside the control module. The fuel enters the control module. The fuel from the fuel transfer pump enters the control module at fuel inlet (3). The fuel exits the control module at fuel outlet (1). The ECM can also be air cooled.

The personality module consists of the following items:

• The personality module has all of the software and instructions for the ECM. Updating the personality module to a different version may cause some changes. Some of the characteristics of the engine operation may behave differently.

• A control map defines the fuel rate, the timing, and other similar values. These values are defined for various operating conditions in order to achieve the optimum engine performance and fuel consumption. These values are programmed into the personality module at the factory.

The ECM consists of the following items:

• The ECM has a microprocessor that is used to perform computing functions. The microprocessor is necessary for the ECM to execute the following functions: governing, injection timing control, system diagnostics and data link communications. The microprocessor receives instructions from the software that is stored in the personality module.

• The ECM has a permanent memory that is used to store programmable parameters and diagnostic codes.

• Input circuits filter electrical noise from the sensor signals. Input circuits protect the internal circuits of the ECM from potentially damaging voltage levels.

• Output circuits provide the high currents that are necessary to energize the injector solenoids, the lamps, and relays.