1. Computers
Chapter Lesson 4

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

3. 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)

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

5. 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

6. 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

7. 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.

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

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

10. 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

11. Parts of a Computer

12. 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)

13. 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

14. 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

15. 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

16. 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

17. Computer Data Flow

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

19. 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

20. 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

21. 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

22. 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

23. 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

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

25. 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

26. Multiple Sensor Inputs

27. 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