Unit 2 Computer Systems

1. Unit 2 Computer Systems History of Computers in Automobiles

2. Computer Advantages • On-board diagnostics • Increased driver convenience • Improved passenger safety • Compensation for component or engine wear

3. History of Computers • Computers were introduced in the late 70’s by Chrysler called Lean Burn • Lean Burn only adjusted ignition spark timing by retarding the timing to reduce emissions and advance timing during acceleration • OBD was also introduced in 1979 that would use a feedback carburetor system

4. OBD1 • An On Board Diagnostic System gives you the general idea what is wrong with the Sensors or Outputs • Used multiple software and Data link connector harnesses • Data link connectors varied in location with automakers

5. OBDII • All vehicles from 1996 and up use this system • A global system with one Data Link connector, and located under the dash • All codes are 3 digits and are internationally defined

6. Cybernetics

7. Class work • Look at sensors, CPU, and Actuators • Location

8. Computer Signals • Computer signal • voltage variation over short periods of time • specific arrangement of pulses or waves used to carry data, or information • Computer signals can be digital or analog

9. Binary Code

10. Digital Signal On-off signal like that produced by a rapidly flipping switch

11. Analog Signal Gradually changes in strength like the output from a dimming switch

12. Computer System Operation • There are three stages of computer system operation: • input • processing and storage • output

13. Inputs and Outputs

14. Computer System Block Diagram Fig 18

15. Sensor Locations • Sensors can be found almost anywhere on a vehicle: • on the engine • on or in the transmission or transaxle • in the exhaust system • on the wheel hubs • on and in the fuel tank • on the suspension • in the trunk

16. Sensor Locations Some of the sensors located on the engine and transaxle

17. Sensor Classifications • Sensors can be classified into two general categories: • active sensors • passive sensors

18. Active Sensor

19. Magnetic Sensor • Also called a permanent magnet (PM) generator • Uses part movement and induced current to produce a signal • Produces an analog signal • Used to monitor speed or part rotation • Vehicle speed and wheel speed sensors are often magnetic sensors

20. Reference Voltage • Applied to a sensor by the computer • Usually 5 volts on most vehicles • Computer steps down battery voltage so that a smooth, constant supply of dc voltage is fed to passive sensors • Sensor alters the reference voltage by changing is internal resistance

21. Passive Sensor

22. Sensor Types • Common sensors used in late-model vehicles: • Intake air temperature sensor (IAT) • measures the temperature of intake air as it enters the intake manifold • Engine coolant temperature sensor (ECT) • measures the temperature of engine coolant

23. Sensor Types • Oxygen sensors • measure the amount of oxygen in the engine’s exhaust gases • Manifold absolute pressure sensor (MAP) • measures the pressure inside the engine intake manifold • Barometric pressure sensor (BARO) • measures the outside air pressure

24. Sensor Types • Throttle position sensor (TP) • measures the opening angle of the throttle valves to detect driver power demand • Engine speed sensor • measures engine rpm • Crankshaft position sensor (CKP) • measures crankshaft position and speed

25. Sensor Types • Camshaft position sensor (CMP) • measures camshaft position and rotation • Mass airflow sensor (MAF) • measures the amount of intake air flowing into the engine • Knock sensor (KS) • detects engine pinging, preignition, or detonation

26. Sensor Types • Oil level sensor • measures the amount of oil in the engine oil pan • EGR sensor • measures the position of the exhaust gas recirculation valve pintle • Impact sensors • detect a collision for the air bag system

27. Sensor Types • Vehicle speed sensors (VSS) • measures the vehicle’s road speed • Fuel tank pressure sensor • measures fuel tank pressure as part of some evaporative emission control systems • Battery temperature sensor • monitors battery temperature for charging system functions

28. Computer Names • Automobile manufacturers have many names for their computers • Here are nine of those names: • Central processing unit (CPU) • Electronic control unit (ECU) • Electronic control module (ECM) • Engine control module (ECM)

29. Computer Types • Several types of computers can be used in a car • The most common types are: • Vehicle control module • coordinates engine, transmission, traction control, and anti-lock brake functions • Powertrain control module • used to monitor and control the engine and transmission

30. Computer Types • Engine control module • used to control engine management functions • Anti-lock brake module • used to control anti-lock brake operation • Instrumentation module • used to operate a digital dash display

31. Computer Types • Air bag module • controls the vehicle’s air bag system • High-power module • used to control high current signals for outputs • Body module • coordinates body functions such as lighting, radio, driver’s information center, electronic compass, etc.

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

33. Computer Data Flow

34. RAM • Random access memory • Read and write type memory • Stores information or data temporarily • Data is erased if battery power is removed

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

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

37. 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

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

39. 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

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

41. Actuators • Devices which allow the computer to do work and alter the operation of other components • Actuators may be found anywhere on the modern automobile

42. Actuator Operation • When the computer turns on an actuator, it normally provides the device with a ground circuit • Current can then operate the actuator

43. Relay Operation

44. Specific Actuators • Common actuators used on modern vehicles include: • Fuel injector • solenoid valve that controls fuel flow • Fuel pump • electric motor-driven pump

45. Specific Actuators • Idle air solenoid • controls airflow into the engine to control idle speed • Idle speed motor • reversible dc motor that opens and closes the throttle valve to control idle speed • EGR solenoids • open and close small ports to control exhaust gas flow back into the engine

46. Specific Actuators • Ignition coil • changes low voltage into high voltage that operates the spark plugs • Ignition module • uses computer circuits that control the operation of the ignition coils