C-10 and C-12 Truck Engines Caterpillar

Illustration 1	g00416682
Top View (1) Speed sensor or timing sensor (2) Coolant temperature sensor (3) Inlet air temperature sensor (4) Boost sensor (5) Fuel temperature sensor (6) Atmospheric pressure sensor

Illustration 2	g00416684
Front View (1) Speed sensor or timing sensor (2) Coolant temperature sensor (5) Fuel temperature sensor

Illustration 3	g00416687
Right Side View (7) Oil pressure sensor

Illustration 4	g00416689
Left Side View (5) Fuel temperature sensor (6) Atmospheric pressure sensor (8) Engine wiring harness (9) Electronic Control Module (ECM)

The electronic control system has the following major components:

• (1) Speed sensor or timing sensor

• (2) Coolant temperature sensor

• (3) Inlet air temperature sensor

• (4) Boost sensor

• (5) Fuel temperature sensor

• (6) Atmospheric pressure sensor

• (7) Oil pressure sensor

• (8) Engine wiring harness

• (9) Electronic Control Module (ECM)

• A remote mounted throttle position sensor

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 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 Systems Operation/Testing And Adjusting, "Unit Injector" for a complete explanation of the fuel injection process.

The engine uses the following three types of electronic components:

• input

• control

• output

An input component is one that sends an electrical signal to the electronic control module of the system. The signal that is sent varies in either voltage or frequency. The variation of the signal is in response to a change in some specific system of the vehicle. The electronic control module sees the input sensor signal as information about the condition, environment, or operation of the vehicle.

A control component receives the input signals. Electronic circuits inside the control 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 group. 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. A moving solenoid plunger will perform work. By performing work, the component has functioned in order to regulate the vehicle.

2. 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:

• improvement in performance

• improvement in fuel consumption

• reduction in emissions levels