Computers Chapter 17 Lesson 4

Computers The term computer refers to any electronic circuit configuration that can use multiple inputs to determine outputs

Computer Names Automobile manufacturers have many names for their computers: central processing unit (CPU) electronic control unit (ECU) electronic control module (ECM) engine control module (ECM)

Computer Names (continued) electronic control assembly (ECA) powertrain control module (PCM) vehicle control module (VCM) microprocessor logic module

Computer Types Engine control module Anti-lock brake module controls engine management functions Anti-lock brake module controls anti-lock brake operation Instrumentation module operates the digital dash display

Computer Types Ignition module Suspension system module controls ignition functions, such as timing Suspension system module controls ride stiffness or shock absorber action Climate control module controls the operation of the heating, ventilation, and air conditioning systems

Computer Types Air bag module High-power module Body module controls the vehicle’s air bag system High-power module Controls current or processes output signals from a few sensors and the main computer Body module coordinates body functions, such as lighting, radio, driver’s information center, electronic compass, etc.

Computers may be located almost anywhere on the vehicle Computer Locations Computers may be located almost anywhere on the vehicle

Computer Construction Computers are composed of printed circuit boards, integrated circuits, capacitors, resistors, transistors, and other electronic components

Parts of a Computer A computer can be divided into 11 basic parts: voltage regulator amplifiers conditioners buffer microprocessor memory clock output drivers circuit board harness connector computer housing

Parts of a Computer

Voltage Regulator Provides a reduced voltage for the components in the computer and sensors Provides a smooth dc voltage that does not vary and is free of any spikes (abrupt changes in voltage)

Computer Amplifier Strengthens various signals when inside the computer amplifier might increase the voltage signal from the oxygen sensor, which is less than one volt Allows a low voltage signal to be used by the circuits in the computer

Input Conditioner Also called a converter or interface Alters the input signals from some sensors Modifies incoming data so that it can be utilized by the computer Converts analog signals to digital signals

Output Conditioner Also called a converter or interface Changes output signals from digital to analog Allows the operation of actuators Protects the computer processor from high current

Microprocessor Integrated circuit capable of analyzing data and calculating appropriate outputs Uses the binary number system to make decisions, comparisons, or calculations Compares input signals to memory data to decide what the outputs should be for maximum efficiency

Computer Data Flow

RAM Random access memory Stores information or data temporarily Data is erased if battery power is removed

ROM Read only memory Stores permanent data that cannot be removed from memory Contains calibration tables and lookup tables for the general vehicle make and model

PROM Programmable read only memory Contains permanent data that is more specific than the data stored in ROM engine and transaxle specifications, vehicle weight, and tire size are specifics found in the PROM May be replaced or reprogrammed to upgrade vehicle operation

EPROM Erasable programmable read only memory Can be changed, usually by the manufacturer using special equipment Used for storing odometer readings on an electronic dash display

EEPROM Electrically erasable programmable read only memory Can be altered by the technician in the field Allows the manufacturer to change operating parameters if a performance or driveability problem is discovered

Other Memories Flash erasable programmable read only memory (FEPROM) similar to EEPROMs in all respects Keep alive memory (KAM) memory chip that allows the computer to have an adaptive strategy stores calibration information that enhances vehicle operation as parts wear

Output Drivers Control current flow through the actuators When energized by the computer, drivers ground the actuator circuits, providing actuator operation

Multiple Sensor Inputs Computer system uses inputs from more than one sensor to make most control decisions Fuel injection example: engine coolant temperature sensor signals a cold engine computer would use both speed and temperature signals to increase injector pulse width to enrich the mixture for cold engine operation

Multiple Sensor Inputs

Computer Network Series of computers that control different systems but work together to improve overall vehicle efficiency Shares wires, input signals, and output signals Computers exchange data from sensors to prevent duplication of parts and to reduce wiring