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CBCJH COMPUTERS AND INPUT SENSORS CHAPTER 8. CBCJH VOLTAGE SIGNALS l ANALOG VOLTAGE SIGNALS –VARIABLE VOLTAGE SIGNAL –COMPUTERS INPUTS ARE USUALLY ANALOG.

Dec 23, 2015

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  • Slide 1
  • CBCJH COMPUTERS AND INPUT SENSORS CHAPTER 8
  • Slide 2
  • CBCJH VOLTAGE SIGNALS l ANALOG VOLTAGE SIGNALS VARIABLE VOLTAGE SIGNAL COMPUTERS INPUTS ARE USUALLY ANALOG TYPE SIGNALS EASY TO DIAGNOSE WITH DVOM DIRECT CURRENT OR ALTERNATING CURRENT Pg 153C
  • Slide 3
  • CBCJH DIGITAL VOLTAGE SIGNALS l VOLTAGE IS EITHER HIGH OR LOW IN A GIVEN TIME PERIOD l COMPUTER USES AND PROCESSES INFORMATION IN DIGITAL LANGUAGE (BINARY 0 or 1) l SOME INPUTS PRODUCE A SQUARE WAVE SIGNAL Pg 154C
  • Slide 4
  • CBCJH COMPUTER OPERATION l INPUT CONDITIONING AMPLIFICATION ANALOG TO DIGITAL CONVERSION SOME A/D CONVERTER EXTERNAL TO MAIN PROCESSOR. (LIKE FORD PROGRAMMABLE SPEED ONLY MEMORY - PSOM) Pg 155C
  • Slide 5
  • CBCJH COMPUTER MEMORY l RAM - RANDOM ACCESS MEMORY TEMPORARY STORAGE VOLATILE OR NON-VOLATILE l ROM - READ ONLY MEMORY l PROM - PROGRAMMABLE READ ONLY MEMORY TELLS MICROPROCESSOR HOW VEHICLE IS EQUIPPED Pg 159C
  • Slide 6
  • CBCJH COMPUTER PROGRAMMED STRATEGY l OPEN LOOP - CLOSED LOOP l ADAPTIVE STRATEGY ABILITY OF COMPUTER TO LEARN FROM PAST EXPERIENCE. COMPENSATES FOR WEAR u Will lose learned strategy if: BATTERY DISCONNECTED WHEN MAJOR COMPONENT REPLACED NEW VEHICLE Pg 160C
  • Slide 7
  • CBCJH INPUT PROCESSING l ROM LOOK UP TABLES (Pg 162C) l COMPUTER TAKES ALL INPUT INFO BEFORE MAKING DECISION l ONE WIRE INPUT (Pg 140L & 154L) l TWO WIRE INPUT (Pg 142L & 143L) l THREE WIRE INPUT (Pg 144L) l FOUR WIRE INPUT (Pg 146L)
  • Slide 8
  • CBCJH PINPOINT TESTING l MOST REPAIR MANUALS TELL TO CAUSE OPPOSITE CODE l OHMMETER VS. VOLTMETER l FREQUENCY INPUT TESTING l LAB SCOPE USE l BLOCK LEARN - INTEGRATOR
  • Slide 9
  • CBCJH OXYGEN SENSORS l 1,2,3,4 Wire s l EGO, HEGO l Lean Low Volts l Rich High Volts l Zirconia Type l Titania Type l DVOM or Lab Scope Only!!! PAGE 168C
  • Slide 10
  • CBCJH ECT/ACT SENSORS l THERMISTORS HIGH RESISTANCE COLD AND LOWER RESISTANCE HOT PG 142L
  • Slide 11
  • CBCJH THROTTLE POSITION SENSORS (TPS) l ROTARY AND LINEAR l MUST BE SMOOTH VOLTAGE CHANGE l BEST TO USE A LAB SCOPE FOR TEST PG 145L
  • Slide 12
  • CBCJH THROTTLE SWITCH l Four Wire Sensor l Used on alot of Foreign Cars and Trucks l Adjustment is critical l Some switches used as Fuel Pump Shut Off Pg 146L
  • Slide 13
  • CBCJH MANIFOLD ABSOLUTE PRESSURE SENSOR l Senses differences between atmospheric pressure and manifold vacuum. l Must use specialized equipment to test l Sometimes used for BARO Input information Pg 147L
  • Slide 14
  • CBCJH MASS AIR FLOW SENSORS l VANE TYPE l Commonly used on foreign Cars l Test with DVOM or Lab Scope l Plate movement proportional to Air Flow l Other Inputs l HOT WIRE TYPE or GRID TYPE l Use Frequency Test l Map Frequency should always be a straight line transition with rpm. l Tap Test Pg 151L Pg 152L
  • Slide 15
  • CBCJH KNOCK SENSORS l PIEZOELECTRIC CRYSTAL l Produces a frequency and changes it to a voltage before sending to PCM l TAP TEST, DVOM, FREQ or OHMMETER
  • Slide 16
  • CBCJH EGR SENSORS l EVP Linear Sensor l Must test mechanical and electrical l Many different types of EGR & ``EGR Controls and EGR Sensors l Most EVPs send a Analog signal l Lots of Driveability Problems l EGR problems can be caused by other Inputs Pg 154L Pg 317L
  • Slide 17
  • CBCJH VEHICLE SPEED SENSORS l AC SIGNAL (ANALOG) l LOCATED DIFFERENT PLACES l SPEED BUFFER OR PSOM l CAN CAUSE TCC, CRUISE, SPEEDOMETER PROBLEMS
  • Slide 18
  • CBCJH NEUTRAL DRIVE SWITCH
  • Slide 19
  • CBCJH OUTPUTS l ACTUATORS SOLENOIDS RELAYS DISPLAYS l CONTROLLED BY DRIVERS l TRANSISTORS OR GROUPS OF TRANSISTORS
  • Slide 20
  • CBCJH STUDY HARD AND ABSORB!!