CBC CBC JHJH
COMPUTERS AND INPUT COMPUTERS AND INPUT SENSORSSENSORS
CHAPTER 8CHAPTER 8
CBC CBC JHJH
VOLTAGE SIGNALSVOLTAGE SIGNALS
ANALOG VOLTAGE SIGNALSANALOG VOLTAGE SIGNALS– VARIABLE VOLTAGE SIGNALVARIABLE VOLTAGE SIGNAL– COMPUTERS INPUTS ARE USUALLY COMPUTERS INPUTS ARE USUALLY
ANALOG TYPE SIGNALSANALOG TYPE SIGNALS– EASY TO DIAGNOSE WITH DVOMEASY TO DIAGNOSE WITH DVOM– DIRECT CURRENT OR ALTERNATING DIRECT CURRENT OR ALTERNATING
CURRENTCURRENT
Pg 153CPg 153C
CBC CBC JHJH
DIGITAL VOLTAGE DIGITAL VOLTAGE SIGNALSSIGNALS
VOLTAGE IS EITHER HIGH OR LOW VOLTAGE IS EITHER HIGH OR LOW IN A GIVEN TIME PERIODIN A GIVEN TIME PERIOD
COMPUTER USES AND PROCESSES COMPUTER USES AND PROCESSES INFORMATION IN DIGITAL INFORMATION IN DIGITAL LANGUAGE (BINARY 0 or 1)LANGUAGE (BINARY 0 or 1)
SOME INPUTS PRODUCE A SQUARE SOME INPUTS PRODUCE A SQUARE WAVE SIGNAL WAVE SIGNAL
Pg 154CPg 154C
CBC CBC JHJH
COMPUTER OPERATIONCOMPUTER OPERATION
INPUT CONDITIONINGINPUT CONDITIONING– AMPLIFICATIONAMPLIFICATION– ANALOG TO DIGITAL CONVERSIONANALOG TO DIGITAL CONVERSION– SOME A/D CONVERTER EXTERNAL TO SOME A/D CONVERTER EXTERNAL TO
MAIN PROCESSOR. (LIKE FORD MAIN PROCESSOR. (LIKE FORD PROGRAMMABLE SPEED ONLY PROGRAMMABLE SPEED ONLY MEMORY - PSOM)MEMORY - PSOM)
Pg 155CPg 155C
CBC CBC JHJH
COMPUTER MEMORYCOMPUTER MEMORY
RAM - RANDOM ACCESS MEMORYRAM - RANDOM ACCESS MEMORY– TEMPORARY STORAGETEMPORARY STORAGE– VOLATILE OR NON-VOLATILEVOLATILE OR NON-VOLATILE
ROM - READ ONLY MEMORYROM - READ ONLY MEMORY PROM - PROGRAMMABLE READ PROM - PROGRAMMABLE READ
ONLY MEMORYONLY MEMORY– TELLS MICROPROCESSOR HOW TELLS MICROPROCESSOR HOW
VEHICLE IS EQUIPPEDVEHICLE IS EQUIPPED
Pg 159CPg 159C
CBC CBC JHJH
COMPUTER COMPUTER PROGRAMMED STRATEGYPROGRAMMED STRATEGY OPEN LOOP - CLOSED LOOPOPEN LOOP - CLOSED LOOP ADAPTIVE STRATEGYADAPTIVE STRATEGY
– ABILITY OF COMPUTER TO LEARN ABILITY OF COMPUTER TO LEARN FROM PAST EXPERIENCE.FROM PAST EXPERIENCE.
– COMPENSATES FOR WEARCOMPENSATES FOR WEAR Will lose learned strategy if: Will lose learned strategy if:
– BATTERY DISCONNECTEDBATTERY DISCONNECTED
– WHEN MAJOR COMPONENT REPLACEDWHEN MAJOR COMPONENT REPLACED
– NEW VEHICLENEW VEHICLE
Pg 160CPg 160C
CBC CBC JHJH
INPUT PROCESSINGINPUT PROCESSING
ROM LOOK UP TABLES (Pg 162C)ROM LOOK UP TABLES (Pg 162C) COMPUTER TAKES ALL INPUT COMPUTER TAKES ALL INPUT
INFO BEFORE MAKING DECISIONINFO BEFORE MAKING DECISION ONE WIRE INPUT (Pg 140L & 154L)ONE WIRE INPUT (Pg 140L & 154L) TWO WIRE INPUT (Pg 142L & 143L)TWO WIRE INPUT (Pg 142L & 143L) THREE WIRE INPUT (Pg 144L)THREE WIRE INPUT (Pg 144L) FOUR WIRE INPUT (Pg 146L)FOUR WIRE INPUT (Pg 146L)
CBC CBC JHJH
PINPOINT TESTINGPINPOINT TESTING
MOST REPAIR MANUALS TELL TO MOST REPAIR MANUALS TELL TO CAUSE OPPOSITE CODECAUSE OPPOSITE CODE
OHMMETER VS. VOLTMETEROHMMETER VS. VOLTMETER FREQUENCY INPUT TESTINGFREQUENCY INPUT TESTING LAB SCOPE USELAB SCOPE USE BLOCK LEARN - INTEGRATORBLOCK LEARN - INTEGRATOR
CBC CBC JHJH
OXYGEN SENSORSOXYGEN SENSORS
1,2,3,4 Wire s1,2,3,4 Wire s EGO, HEGOEGO, HEGO Lean Low VoltsLean Low Volts Rich High VoltsRich High Volts Zirconia TypeZirconia Type Titania TypeTitania Type DVOM or Lab Scope DVOM or Lab Scope
Only!!!Only!!! PAGE 168CPAGE 168C
CBC CBC JHJH
ECT/ACT SENSORSECT/ACT SENSORS
THERMISTORS HIGH RESISTANCE THERMISTORS HIGH RESISTANCE COLD AND LOWER RESISTANCE HOTCOLD AND LOWER RESISTANCE HOT
PG 142LPG 142L
CBC CBC JHJH
THROTTLE POSITION THROTTLE POSITION SENSORS (TPS)SENSORS (TPS)
ROTARY AND LINEARROTARY AND LINEAR MUST BE SMOOTH VOLTAGE CHANGEMUST BE SMOOTH VOLTAGE CHANGE BEST TO USE A LAB SCOPE FOR TESTBEST TO USE A LAB SCOPE FOR TEST
PG 145LPG 145L
CBC CBC JHJH
THROTTLE SWITCHTHROTTLE SWITCH
Four Wire SensorFour Wire Sensor Used on alot of Foreign Cars and TrucksUsed on alot of Foreign Cars and Trucks Adjustment is criticalAdjustment is critical Some switches used as Fuel Pump Shut Off Some switches used as Fuel Pump Shut Off
Pg 146LPg 146L
CBC CBC JHJH
MANIFOLD ABSOLUTE MANIFOLD ABSOLUTE PRESSURE SENSORPRESSURE SENSOR
Senses differences between atmospheric Senses differences between atmospheric pressure and manifold vacuum.pressure and manifold vacuum.
Must use specialized equipment to testMust use specialized equipment to test Sometimes used for BARO Input informationSometimes used for BARO Input information
Pg 147LPg 147L
CBC CBC JHJH
MASS AIR FLOW SENSORSMASS AIR FLOW SENSORS
VANE TYPEVANE TYPE Commonly used on Commonly used on
foreign Carsforeign Cars Test with DVOM or Test with DVOM or
Lab ScopeLab Scope Plate movement Plate movement
proportional to Air proportional to Air FlowFlow
Other InputsOther Inputs
HOT WIRE TYPE HOT WIRE TYPE or GRID TYPEor GRID TYPE
Use Frequency Test Use Frequency Test Map Frequency Map Frequency
should always be a should always be a straight line straight line transition with rpm.transition with rpm.
Tap TestTap Test
Pg 151LPg 151L Pg 152LPg 152L
CBC CBC JHJH
KNOCK SENSORSKNOCK SENSORS
PIEZOELECTRIC CRYSTALPIEZOELECTRIC CRYSTAL Produces a frequency and changes it to a Produces a frequency and changes it to a
voltage before sending to PCMvoltage before sending to PCM TAP TEST, DVOM, FREQ or OHMMETER TAP TEST, DVOM, FREQ or OHMMETER
CBC CBC JHJH
EGR SENSORSEGR SENSORS EVP Linear SensorEVP Linear Sensor Must test mechanical and electricalMust test mechanical and electrical Many different types of EGR & ``EGR Many different types of EGR & ``EGR
Controls and EGR SensorsControls and EGR Sensors Most EVP’s send a Analog signalMost EVP’s send a Analog signal Lots of Driveability ProblemsLots of Driveability Problems EGR problems can be caused by other EGR problems can be caused by other
InputsInputs
Pg 154LPg 154LPg 317LPg 317L
CBC CBC JHJH
VEHICLE SPEED SENSORSVEHICLE SPEED SENSORS
AC SIGNAL (ANALOG)AC SIGNAL (ANALOG) LOCATED DIFFERENT PLACESLOCATED DIFFERENT PLACES SPEED BUFFER OR PSOMSPEED BUFFER OR PSOM CAN CAUSE TCC, CRUISE, SPEEDOMETER CAN CAUSE TCC, CRUISE, SPEEDOMETER
PROBLEMSPROBLEMS
CBC CBC JHJH
NEUTRAL DRIVE SWITCHNEUTRAL DRIVE SWITCH
CBC CBC JHJH
OUTPUTSOUTPUTS
ACTUATORSACTUATORS– SOLENOIDSSOLENOIDS– RELAYSRELAYS– DISPLAYS DISPLAYS
CONTROLLED BY DRIVERSCONTROLLED BY DRIVERS TRANSISTORS OR GROUPS OF TRANSISTORS OR GROUPS OF
TRANSISTORSTRANSISTORS
CBC CBC JHJH
STUDY HARD AND STUDY HARD AND ABSORB!!ABSORB!!
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