chap53 pps Automotive technology at University of Cambridge

start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 53, the reader should be able to: • • • Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “A” (General Electrical/Electronic Systems Diagnosis) Explain the purpose and function of onboard computers List the various parts of an automotive computer Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 53, the reader should be able to: • • List five input sensors List four devices controlled by the computer (output devices) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: actuator • analog-to-digital (AD) converter binary central processing unit (CPU) • clock generator • controller • controller area network (CAN) digital • duty cycle EEPROM • E2 PROM • electronic control assembly (ECA) • electronic control module (ECM) • electronic control unit (ECU) • engine mapping Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: high-side drivers (HSD) input conditioning keep-alive memory (KAM) low-side drivers (LSD) multiplexing • network • nonvolatile output drivers Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: power train control module (PCM) • programmable readonly memory (PROM) Random-access memory (RAM) • read-only memory (ROM) serial data • splice pack terminating resistors • volatile Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 COMPUTER CONTROL Modern automotive control systems consist of a network of  electronic sensors, actuators, and computer modules designed to  regulate the power train and vehicle support systems. The power  train control module (PCM) is the heart of this system. It  coordinates engine and transmission operation, processes data,  maintains communications, and makes the control decisions needed  to keep the vehicle operating Automotive computers use voltage to send and receive information.  It converts input or data into voltage signal combinations that  represent a variety of information—temperature, speed, or even  words and letters, and then delivers the data in computed or  processed form Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 THE FOUR BASIC COMPUTER FUNCTIONS Operation of a computer can be divided into four basic functions: Input Processing Storage Output  Figure 53–1 All computer systems perform four basic functions: input, processing, storage, and output Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Input  First, the computer receives a voltage signal (input) from an  input device. The device can be as simple as a button or a switch on  an instrument panel, or a sensor on an automotive engine.  Vehicles use mechanical, electrical, and magnetic sensors to  measure factors such as speed, engine RPM, air pressure, oxygen  content of exhaust gas, airflow, and engine coolant temperature.  Figure 53–2 A potentiometer uses a movable contact to vary resistance and send an analog voltage to the PCM The signals must  undergo input  conditioning.  Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Processing  Input voltage signals received by a computer are  processed through a series of electronic logic circuits maintained in  its programmed instructions. These logic circuits change the input  voltage signals, or data, into output voltage signals or commands Storage  The program instructions for a computer are stored in  electronic memory. Some programs may require that certain input  data be stored for later reference or future processing. In others,  output commands may be delayed or stored before they are  transmitted to devices elsewhere in the system Computers have two types of memory: permanent and temporary.  Permanent memory is called read­only memory (ROM) because  the computer can only read the contents; data is retained even when  power to the computer is shut off Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SAE COMMUNICATION CLASSIFICATIONS The Society of Automotive Engineers (SAE) standards include  three categories of in­vehicle network communications, including: Class A  Low­speed networks (less than 10,000 bits per second [10  kbs]) are generally used for trip computers, entertainment, and other  convenience features. Most low­speed Class A communication  functions are performed using the following: UART standard (Universal Asynchronous Receive/Transmit)  used by GM (8192 bps) CCD (Chrysler Collision Detection) by Chrysler (7812.5 bps) NOTE: The “collision” in CCD­type bus communication refers to the  program that avoids conflicts of information exchange within the bus, and does not refer to airbags or other accident­related circuits of the vehicle Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Chrysler SCI (Serial Communications Interface) is used  tocommunicate between the engine controller and a scan tool  (62.5 kbps) ACP (Audio Control Protocol) is used for remote control of  entertainment equipment (twisted pairs) on Ford vehicles Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Class B  Medium­speed networks (10,000 to 125,000 bits per  second [10 to 125 kbs]) are generally used for information transfer  among modules, such as instrument clusters, temperature sensor  data, and other general uses General Motors GMLAN; both low­and medium­speed and  Class 2, which uses 0­to 7­volt pulses with an available pulse  width. Meets SAE 1850 variable pulse width (VPW) Chrysler Programmable Communication Interface (PCI). Meets  SAE standard J­1850 pulse width modulated (PWM) Ford Standard Corporate Protocol (SCP). Meets SAE  standardJ­1850 pulse width modulated (PWM) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Class C High­speed networks  (125,000+ bits per second)  are generally used for real­ time power train and  vehicle dynamic control.  Figure 53–17 A typical bus system showing module CAN communications and twisted pairs of wire Most high­speed bus  communication is  controller area network  or CAN.  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 What is a Bus? A bus is a term used to describe a communication network Therefore, there are connections to the bus and bus communications, both of which refer to digital messages being transmitted among electronic modules or computers Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 MODULE COMMUNICATION DIAGNOSIS Most vehicle manufacturers specify a scan tool be used to diagnose  modules and communications.  Some tests of the communication  bus (network) and some of the service procedures require a DMM,  set to DC volts, to monitor communications. Variable voltage  indicates messages are being sent and received Most high­speed bus systems use resistors at each end called  terminating resistors to help reduce interference into other  systems in the vehicle.  Usually two 120­ohm resistors are installed  at each end and connected electrically in parallel. Two 120­ohm  resistors connected in parallel would measure 60 ohms if being  tested using an ohmmeter See Figure 53–18 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 53–18 Checking the terminating resistors using an ohmmeter at the DLC Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBD II DATA LINK CONNECTOR All OBD II vehicles use a 16­pin connector that includes:  Pin 4 = chassis ground Pin 5 = signal ground Pin 16 = battery power                (4A max) Figure 53–19 Sixteen-pin OBD II DLC with terminals identified Scan tools use the power pin (16) ground pin (4) for power so that a separate cigarette lighter plug is not necessary on OBD II vehicles Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Vehicles may use one of two major standards including: ISO 9141­2 Standard (ISO = International Standards Organization) Pins 7 and 15 (or wire at pin 7 and no pin at 2 or a wire at 7 and at 2 and/or 10) SAE J­1850 Standard (SAE = Society of Automotive Engineers) Two types: VPW (variable pulse width) PWM (pulse width modulated) Pins 2 and 10 (no wire at pin 7) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 General Motors vehicles use: SAE J­1850 (VPW—Class 2—10.4 kb) standard, which uses pins 2, 4, 5, and 16 and not 10 GM Domestic OBD II Pin 1 and 9—CCM (Comprehensive Component Monitor) slow  baud rate—8192 UART Pins 2 and 10—OEM Enhanced—Fast Rate—40,500 baud rate Pins 7 and 15—Generic OBD II—ISO 9141—10,400 baud rate  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Chrysler, European, and Asian vehicles use: ISO 9141­2 standard uses pins 4, 5, 7, 15, and 16 Chrysler OBD II Pins 2 and 10—CCM Pins 3 and 14—OEM Enhanced—60,500 baud rate Pins 7 and 15—Generic OBD II ­ ISO 9141—10,400 baud rate  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Ford vehicles use: SAE J­1850(PWM) (PWM—41.6 kb) standard, which uses pins 2, 4, 5, 10, and 16 Ford Domestic OBD II Pins 2 and 10—CCM Pins 6 and 14—OEM Enhanced—Class C—40,500 baud rate  Pins 7 and 15—Generic OBD II—ISO 9141—10,400 baud rate  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY The Society of Automotive Engineers (SAE) standard J­1930  specifies that the term power train control module (PCM) be used  for the computer that controls the engine and transmission in a  vehicle The four basic computer functions include input, processing,  storage, and output Read­only memory (ROM) can be programmable (PROM),  erasable (EPROM), or electrically erasable (EEPROM) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Computer input sensors include engine speed (RPM), MAP,  MAF, ECT, O2S, TP, and VS A computer can only turn a device on or turn a device off, but  it can do the operation very rapidly Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458