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Chapter 

C

: Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair

61

lization. Most of the sensors are resistors. Voltage sig-
nals from the sensors to the computer change accord-
ing to resistance changes. Three factors can change re-
sistance:

• Air or fuel pressure
• Air or coolant temperature
• Physical motion

Determine the operation and condition of a sensor or
actuator by measuring resistance through the unit and
the resistance between the sensor and ground with an
ohmmeter. Do not overlook the circuit. Electronic prob-
lems are often caused by poor connections or damaged
wiring. Always test the circuit first.

A high-impedance digital multimeter (DMM) or oscillo-
scope can be used to measure supply and ground volt-
age at a sensor, as well as voltage drop across the
sensor. An oscilloscope measures voltage as a function
of time and thus displays signal interference. The aver-
age voltage over the span of a few milliseconds is dis-
played as a trace on the screen.

Component Testing

Before testing individual components on a fuel injected
engine perform a diagnostic test using a scan tool.
Check the PCM for any active or stored codes. If one or
more diagnostic trouble codes are present refer to the
appropriate Service Manual for the correct diagnostic
procedure. Most Service Manuals include information
on diagnosing fuel system problems when no codes are
present. 

Two types of sensors, thermistor and potentiometer, are
commonly used on electronic fuel injection systems.
Actuators are generally either a switch, a relay, or a
solenoid. Both sensors and actuators can be tested
using a DMM or oscilloscope.

A thermistor is a sensor that measures resistance
changes in proportion to temperature, figure 3-13

These sensors have a 2-wire connector: One wire pro-
vides the signal voltage and the other is the return
ground. To check for an internal open or short, connect
the ohmmeter across the 2-wire connector, figure 3-14.

Manufacturers provide specific resistance values for
specific temperatures, as well as voltages, for testing
sensors. Test temperature sensors by immersing them
in water or engine coolant and heating or cooling as re-
quired to determine resistance at specific temperatures.

A potentiometer is a sensor that provides variable resis-
tance across an operational range. It is most often used
as a voltage regulating device. These sensors use a 3-
wire connector to maintain a uniform temperature and
current level across the resistor. One wire supplies the

Fig. 3-13.

Typical thermistor temperature/resistance comparison.

CALIBRATED

SPRINGS

RUBBER

GROMMET

AT PUMP
MODULE

INTERNAL

FUEL FILTER

FUEL FILTER/

FUEL

PRESSURE

REGULATOR

FUEL FLOW TO FUEL

INJECTORS

FUEL INLET

EXCESS FUEL

BACK

TO TANK

Fig. 3-12.

Typical in-tank fuel pressure regulator.

Содержание ASE-A8

Страница 1: ...cedures No warranty can be made from the ideas presented due to personal testing procedures nor does the author or anyone connected with him or her assume any responsibilities or liabilities The use o...

Страница 2: ......

Страница 3: ...ystem Diagnosis and Repair 34 Chapter C Fuel Air Induction and Exhaust Systems Diagnosis and Repair 53 Chapter D Emission Control Systems Diagnosis and Repair 73 Chapter E Computerized Engine Control...

Страница 4: ...ine needed action 9 Diagnose engine mechanical electrical electronic fuel and ignition problems with an oscilloscope engine analyzer and or scan tool determine needed action 10 Prepare and inspect veh...

Страница 5: ...fuel pump assembly inspect service and replace fuel filters 5 Inspect and test electric fuel pump control circuits and components determine needed repairs 6 Inspect test and repair or replace fuel pr...

Страница 6: ...repairs 3 Inspect test and replace canister lines hoses mechanical and electrical components of the evaporative emissions control system E Computerized Engine Controls Diagnosis and Repair Including...

Страница 7: ...ly and replace or repair the right components Improper diagnosis leads to come backs dissatisfied customers a waste of your time and your customer s time Before attempting to repair a performance prob...

Страница 8: ...hemi cal odor Check the temperature gauge for over heating Listen closely to the sound of the exhaust system Be especially conscious of irregular pulses or whistling sounds that may indicate valve pro...

Страница 9: ...DIAGNOSIS Using the Diagnostic System and or a Diagnostic Scan Tool with the appropriate Diagnostic Procedures Manual verify all engine transmission systems are functioning as designed If Diagnostic...

Страница 10: ...damage Do not allow tools to contact exposed terminals when servicing connectors Do not remove components from their protective packaging until necessary These manuals are more in depth than Service M...

Страница 11: ...requency because these parts operate at one half crankshaft speed A stethoscope is a handy tool for isolating noises You can also use a timing light to determine whether a noise is from the top or bot...

Страница 12: ...coolant also produces a distinctive chemical odor Check the temperature gauge for overheating Keep in mind that oil vapor odors are not always the re sult of an internal engine problem A clogged or m...

Страница 13: ...linder Compression Tests The compression test reveals how well each cylinder is sealed by the piston rings valves cylinder head gasket and the spark plug Compression pressure is measured in pounds per...

Страница 14: ...es within these circuits during operation An oscilloscope displays voltage changes during a period of time and is an ideal instrument for testing ignition system operation Traditional automotive oscil...

Страница 15: ...some electronic ignition systems there are no os cillations Firing is displayed as a vertical spike followed by a relatively flat line until the spark ends In parade dis play the height of the oscilla...

Страница 16: ...very small oscillations Intermediate Section The secondary intermediate trace indicates excess coil voltage being dissipated and is similar to that of the pri mary ignition pattern Look for a short v...

Страница 17: ...veal faults in the electronic cir cuits For oscilloscope patterns that indicate fuel prob lems refer to Ignition System Diagnosis discussed pre viously Electrical System Diagnosis Hard starting no sta...

Страница 18: ...ogram is activated and the sequence in which codes are displayed varies between manufacturers The preferred method of DTC retrieval is with a scan tool figure 1 12 However not all systems transmit cod...

Страница 19: ...revent the air injection system from supplying oxygen into the exhaust stream This decreases the amount of O2 at the tailpipe and the efficiency of the converter The air injection system may be disabl...

Страница 20: ...10 12 1 Engine oil diluted w fuel Carburetor idle speed Cold engine Idle mixture too rich Choke stuck shut PCV valve defective Fuel injectors leaking Poor fuel economy Sooty spark black smoke Rough id...

Страница 21: ...hange Possible Decrease Some Increase Some Increase No Change No Change Some to Large Decrease Large Decrease Large Decrease Some Decrease Large Increase No Change No Change Small Decrease Possible No...

Страница 22: ...the profile of the camshaft lobe exactly to provide efficient operation Over the life of an engine valve clearance tends to change as a result of wear on the valve face valve seat pushrod and rocker...

Страница 23: ...d adjustable rocker arms used with hy draulic lifters can also be adjusted with the engine run ning Follow this procedure 1 Starting with any valve back off the rocker arm locknut until the valve star...

Страница 24: ...compressing the hydraulic lifter The pushrod will no longer ro tate freely and the rocker can no longer wiggle from side to side figure 1 18 3 Slowly tighten the rocker arm locknut an additional thre...

Страница 25: ...w ones Make sure both the crankshaft and camshaft re main in the TDC position and all timing marks are aligned during assembly Once the camshaft drive is in place follow the Service Manual procedures...

Страница 26: ...heck using a chemical test kit or exhaust gas analyzer see Book A1 Engine Repair of this series Cooling System Inspection Use a pyrometer to monitor actual engine temperature and eliminate the possibi...

Страница 27: ...cient operat ing temperature In many instances the thermostat is defective and should be replaced Thermostat function can be checked on a running engine Refer to Book A1 Engine Repair in this series f...

Страница 28: ...you have a good understand ing of electrical fundamentals and schematics General ly schematics can be found in the Service Manual although a few manufacturers place them in a separate book In either...

Страница 29: ...s Locator View This column contains the reference to the appropriate locator view Circuit Descriptions The circuit description describes how the system works electrically The circuit description also...

Страница 30: ...be used today only on the minority of batteries that are unsealed and have removable filler caps Some sealed maintenance free batteries are equipped with a built in state of charge indicator in one c...

Страница 31: ...t glove box light underhood light or cigarette lighter remaining on when the vehicle is not in use Parasitic drains required to operate systems that continue to work even when the vehicle is parked an...

Страница 32: ...ding circuit Consult a wiring diagram to determine how power is routed through the circuit then systematically eliminate components to determine which one was remaining on and draining the battery STA...

Страница 33: ...ari ly goes high then settles down to a lower amount sus pect high resistance When high resistance is indicated perform starter cir cuit resistance If testing indicates a starter motor prob lem remove...

Страница 34: ...tests indicate an internal problem the starter motor must be removed from the vehicle and ei ther repaired or replaced Starter Removal The following is a typical starter motor removal se quence Always...

Страница 35: ...arging system includes the generator regulator and all the wiring and connections in the circuit figure 1 36 Charging failure symptoms fit into two categories those that cause the system to Undercharg...

Страница 36: ...accessories it will not be includ ed in the maximum output reading 4 Start the engine and run it at 2 000 RPM or the specified test speed 5 Adjust the carbon pile to obtain the maximum am meter readi...

Страница 37: ...to raise the amper age output This tests the component parts of the exist ing system for proper operation Second Stage Perform this stage if the ammeter reading does not meet specifications during th...

Страница 38: ...s often result from simple and easily corrected problems that become obvious during a quick visual inspection of the system compo nents To begin 1 Check the battery electrolyte level state of charge a...

Страница 39: ...an be performed on a running engine to quickly detect internal problems a Cylinder compression b Cylinder leakage c Cylinder power balance d Oscilloscope 7 When scope testing an ignition system with a...

Страница 40: ...he need for an ignition system that could produce a hotter spark was required The mechanical points could not handle the required increase in current flow To solve this problem the first electronic ig...

Страница 41: ...icient spark intensity Excessive resistance in primary circuit STARTS AND STALLS Engine starts but stalls when the key is released to the RUN position Incorrect ignition timing Deficient spark intensi...

Страница 42: ...y by system Accurate specifications and in structions from the manufacturer are required The fol lowing paragraphs discuss general procedures for test ing a variety of electronic components Electronic...

Страница 43: ...are available start with a setting of approximately 1 4 6mm Crank the engine while observing the spark tester A bright blue spark should be clearly visible Do not crank the engine with the spark plug...

Страница 44: ...es when comparing cylinders in a parade pattern fig ure 2 9 Variations can be caused by fuel or electri cal system problems To separate the two slowly cover the engine air intake to richen the fuel mi...

Страница 45: ...he dis tributor Use the degree scale at the bottom of the screen to read dwell angles SPARK PLUG AND IGNITION CABLE SERVICE Spark plugs are routinely replaced at specific service in tervals as recomme...

Страница 46: ...eignition is usually caused by combustion chamber hot spots or deposits that hold enough heat to prematurely ignite the air fuel charge Crossfiring be tween plug cables or a plug heat range much too h...

Страница 47: ...gapped Do not make gap adjustments by tapping the elec trode on a workbench or other solid object Cleaning the threaded plug holes in the cylinder head with a thread chaser will ensure easy spark plu...

Страница 48: ...le termi nal that looks much like a spark plug The cable end snaps onto the terminal instead of fitting down inside the cap tower When replacing cables disconnect only one cable at a time from a spark...

Страница 49: ...meter lead to the ground side of the component Manufacturers provide voltage drop specifications for various ignition components Measure the voltage drop across the ignition module ground as follows 1...

Страница 50: ...eter lead to the positive bat tery primary terminal of the coil 2 Connect the other ohmmeter lead to the negative distributor primary terminal of the coil The ohmmeter will display primary winding res...

Страница 51: ...well is short at low engine speed and increases as RPM increases The primary circuit does not energize until the module receives a verifiable engine speed signal from the crank shaft position CKP sens...

Страница 52: ...rements Refer to the appropriate Service Manual for the exact description of the system used Testing a Magnetic Sensor Regardless of system design the resistance of a pick up coil can be checked with...

Страница 53: ...nt magnet the magnetic field expands and collapses to produce an analog signal The Hall element contains a logic gate that converts the signal into a digital signal which trig gers transistor switchin...

Страница 54: ...ota tional speed figure 2 26 Like a Hall effect sensor an optical sensor requires an external power source and uses a three wire circuit One wire carries power to op erate the LED one is the signal ge...

Страница 55: ...Chapter B Ignition System Diagnosis and Repair 49 Fig 2 27 The sample vehicle wiring diagram shows PCM sensors actuator and related circuits...

Страница 56: ...emember previous operating condi tions and adapt output commands to the learned characteristics of vehicle operation This feature known as adaptive strategy allows the system to compensate for wear cl...

Страница 57: ...the position of a sweep arm that sends the signal back to the PCM Because the PCM operates on low voltage signals even small changes in resistance anywhere along a circuit can effect system performanc...

Страница 58: ...ightening torque b Over advanced timing c Rich air fuel mixture d Lean air fuel mixture 5 Which of the following spark plug conditions is caused by burning of gasoline additives during normal combusti...

Страница 59: ...battery ground cable before remov ing or replacing fuel system parts to preven acci dental arcing Inspection Because of its many parts and connecting lines the fuel system may develop leaks at severa...

Страница 60: ...TEM IAT SENSOR POOR FUEL ECONOMY SECONDARY IGNITION SYSTEM ECM POWER AND GND CKT ENGING VACUUM FUEL PRESSURE ECT SENSOR THROTTLE POSITION SENSOR MAP SENSOR OXYGEN SENSOR SWITCHING O2S HEATER ENGINE ME...

Страница 61: ...restricted and to require replacement Replacing Inline Filters Disposable inline fuel filters are common and may be used on both carbureted and fuel injected engines The filter may be located in the e...

Страница 62: ...parate the fuel line from the inlet nut plug or cap the line and move it out of the way Remove the fuel inlet nut and lift out the filter and spring figure 3 5 Install the spring and new filter elemen...

Страница 63: ...roperly Re place the pump Volume Test To check fuel pump volume a length of fuel hose and a graduated container are required Disconnect and re move the vacuum pressure gauge but leave the tachometer a...

Страница 64: ...greater than required by the engine For this reason the pressure and volume tests for these pumps measure values other than actual pump output Typically speci fications are provided for checking the s...

Страница 65: ...the new pump on the engine and tighten the mounting bolts to the specified torque value 8 Attach the fuel and vapor lines reinstall parts re moved to gain access and connect the battery ground cable...

Страница 66: ...ng action on the top side The di aphragm relief valve moves opening or closing an ori fice in the fuel chamber to control the amount of fuel re turned to the fuel tank Vacuum acting on the top side of...

Страница 67: ...rvice Manuals include information on diagnosing fuel system problems when no codes are present Two types of sensors thermistor and potentiometer are commonly used on electronic fuel injection systems...

Страница 68: ...sensor or exhaust gas recirculation EGR valve position sensor EVP can be hand operated while checking its resistance A sensor that measures pres sure such as a manifold absolute pressure MAP sensor ca...

Страница 69: ...idth delivers little fuel a longer pulse width de livers more fuel However fuel injectors do not operate at a fixed frequency and their cycle varies with engine speed When the injector opens is determ...

Страница 70: ...For more accurate HO2S test results monitor sensor voltage with an oscilloscope The PCM looks for the oxygen sensor voltage signal to change direction near the 450 mV midpoint of the range Ideally the...

Страница 71: ...ging system is working properly The PCM is receiving the supply voltage it requires Current flow in an injector circuit varies by manufactur er and model year Refer to the appropriate Service Manual f...

Страница 72: ...tors or circuits Low resis tance readings are caused by a short circuit The injector pulse width and duty cycle can be checked with an oscilloscope Be aware with grouped injectors the scope pattern re...

Страница 73: ...element is the only part of the intake air sys tem that requires periodic replacement Although change intervals vary by manufacturer the air filter ele ment on most late model engines is replaced eve...

Страница 74: ...esting the manifold heat control valves Check each component for damage exhaust leakage loose connections and loose mounting Tight en where required The converter or muffler generally is not repaired...

Страница 75: ...upstream from the converter A gauge is attached to the hole and the test is performed When completed a small rivet is driven in the hole to seal the system Temperature Test Before testing repair any k...

Страница 76: ...restriction Carburetor or fuel injection problem Incorrect ignition timing advance or other ignition problem EGR problem Lack of compression or other engine wear Low boost pressure Inspect and correc...

Страница 77: ...e geared together so they ro tate in opposite directions One of the shafts is driven off the crankshaft by a belt The supercharger supplies boost whenever the engine is running Most units use a vacuum...

Страница 78: ...auge readings to a Increase about 5 to 7 psi b Increase about 10 to 15 psi c Decrease about 5 to 7 psi d Decrease about 10 to 15 psi 6 The primary purpose of the pressure regulator in a fuel injection...

Страница 79: ...ent Symptoms of a clogged or damaged PCV system include Increased oil consumption Diluted or contaminated oil Escaping blowby vapors Unstable engine operation at idle and low speed PCV service include...

Страница 80: ...lvent Allow it to drain and dry in the air Do not dry with compressed air this will damage the wire mesh Hose Replacement Any damaged or deteriorated hose must be replaced to ensure proper system oper...

Страница 81: ...e and control the flow of exhaust gasses fig ure 4 6 If the EGR valve fails to open when it should ex pect Increases in NOx formation Pinging and detonation Reduced fuel mileage If the EGR valve leaks...

Страница 82: ...es in the intake manifold and cause a new valve to fail Some EGR valve assemblies can be cleaned and rein stalled Other valve designs cannot be cleaned and must be replaced When cleaning a valve be ca...

Страница 83: ...just ment there are no routine adjustments However man ufacturers do recommend periodic inspections to ensure exhaust emissions are kept within legal limits Inspection Inspect a pump type AIR system a...

Страница 84: ...stricted hose Reconnect the vacuum line increase en gine speed to 2000 RPM then quickly close the throttle Engine speed should stay high for a moment before re turning to idle If not or if the engine...

Страница 85: ...ide and that some of the chips have been drawn into the intake air charge To repair clean the carburetor or throttle body then replace both the hose and the pulse air valve assembly CATALYTIC CONVERTE...

Страница 86: ...urden the catalytic converter Once the test is started the air fuel mixture runs rich and lean and the H02S switches are counted A switch is counted when an oxygen sensor signal goes from below the le...

Страница 87: ...e figure 4 15 The purge valve also may shut off the vapor vent line to the canister whenever the engine is running Check valve operation with a vacuum gauge and pump Whether an electronic solenoid or...

Страница 88: ...hicle without an EVAP leak detection pump sys tem changes in short term memory and movement in target IAC at idle or idle speed change are used to mon itor the system There are two steps for this test...

Страница 89: ...Control NOx emissions 5 Air injection helps to oxidize any unburnt fuel in the exhaust to reduce a Hydrocarbons b Oxides of nitrogen c Carbon dioxide d Carbon monoxide 6 The LDP is designed to a Tran...

Страница 90: ...ure speed distance position pres sure and other factors of engine and vehicle operation The computer processes the voltage signals by com puting the numbers they represent and then delivering output c...

Страница 91: ...promise system operation Conducting a thorough pre liminary evaluation often reveals the cause of or conditions that contribute to common driveability com plaints Prepare the Engine for Testing To tes...

Страница 92: ...ystem or misfire faults 4 Auxiliary emission controls 5 Vehicle speed control and idle control system 6 Computer output circuit faults 7 Transmission 8 Transmission The fourth and fifth characters ind...

Страница 93: ...d drive cycle to be sure the system is fully repaired For example when discovering a code P0125 excessive time to enter closed loop and a code P0155 HO2S 1 Bank 2 Heater Malfunction the best procedure...

Страница 94: ...cumstance under which it was set into memory Hard Codes A hard code indicates a failure that is present at the time of testing and remains permanently in the system until the cause has been repaired I...

Страница 95: ...ly it was most likely an intermittent code To diagnose any DTC go to the test or troubleshooting chart for that particu lar code Pre OBD II vehicles trouble codes should be diagnosed and serviced in a...

Страница 96: ...values that don t logically fit with other powertrain data For instance if the Throttle Position Sensor TPS is reporting wide open but other sensors are reporting idle speed values the ECM will set a...

Страница 97: ...onitoring uses the CKP signal as the primary sensor When a misfire occurs whether due to engine compression ignition or fuel crankshaft speed is affected The ECM is programmed to notice the inter mitt...

Страница 98: ...engine in open loop for several minutes after any start up regardless of HO2S and engine temperatures In addition some sys tems return to open loop at idle and during full throttle acceleration For ac...

Страница 99: ...e A loose or corroded ground connection for a sensor can also force the signal out of range but not far enough to set a code These and similar problems can cause driveability prob lems without setting...

Страница 100: ...ollowing actions Inspect for an engine coolant temperature ECT sensor that has shifted in value Inspect the mass air flow MAF sensor for proper installation Inspect the camshaft position CMP sensor fo...

Страница 101: ...owner Is the A C ON or the Defroster mode ON full time Are the tires at the correct pressure Are the wheels and tires the correct size Are there excessively heavy loads being carried Is the accelerat...

Страница 102: ...her sensing devices in the system fit one of the categories mentioned above Regardless of how a sensor is used you need to know the following to analyze its performance What type of signal it transmit...

Страница 103: ...variable resistor that provides an analog voltage signal to the PCM based on the motion or position of the monitored component Most automotive systems use a potentiometer as a TP sensor to provide a d...

Страница 104: ...PCM The resistance of a piezoresistive crystal changes when pressure is applied to it causing it to produce an ana log signal Capacitive ceramic units use manifold vacu um to vary the distance betwee...

Страница 105: ...stors in the PCM To regulate this voltage drop the coil windings of an actuator must meet a minimum resistance specification If coil resistance is too low higher voltage and current on the ground circ...

Страница 106: ...pare results to specifications Pulse Width Modulation Many automotive solenoids are pulsed on and off rapid ly at a specific number of cycles per second or Hertz Hz The operating cycle of a pulsed sol...

Страница 107: ...e shaft As the armature rotates the pintel moves in or out on the threads depending upon the di rection of the armature These motors contain either two or four coils When two coils are used the PCM co...

Страница 108: ...ariances Diagnostic Scan Tool The diagnostic tools discussed to this point rely on mak ing an actual connection to the circuit or component in question to make a reading In today s vehicles it is ofte...

Страница 109: ...injector pulse width ECT ACT TP sensor signals effect on Idle speed control IAT ECT TP MAP and MAF signals effect on ignition timing control ECT TP sensor and EVP signals effect on EGR control ECT an...

Страница 110: ...uble codes and the idle smoothes out This is usually caused by a poor ground To check voltage drop the circuit must be powered up and have current flowing The circuit also must have the maximum amount...

Страница 111: ...k lead to a good ground and the red lead to the BAT or power terminal on the back of the alternator not the battery figure 5 28 A good alternator should measure less than 0 5 volts AC with the engine...

Страница 112: ...signal voltage of the sensor This ground resistance can offset the signal voltage enough to cause serious drive ability problems For example on a throttle position sensor that operates on a 5 volt re...

Страница 113: ...erates a signal to switch an actuator on and off in a controlled condition While the actuator is being switched perform a wiggle test and take voltmeter readings to pinpoint an intermit tent fault Che...

Страница 114: ...f the actuator is shorted current can ex ceed the maximum safe resistance and internally damage the PCM or ECM Before replacing a PCM or ECM check all output circuits for shorts or low resistance that...

Страница 115: ...ry DTC If the failure does not recur on the next trip the temporary DTC is cleared from memory If the failure does recur on the next trip the ECM will store a DTC and freeze frame and turn on the MIL...

Страница 116: ...omponent Fuel Control and Engine Misfire monitors because they run continuously The readiness status of the following system monitors can be read on the scan tool Oxygen Sensors Oxygen Sensor Heaters...

Страница 117: ...ign what attribute of a speed sensor signal does the PCM process to determine speed a Frequency b Amplitude c Voltage d Duty cycle 8 With the engine operating in closed loop the HO2S signal displayed...

Страница 118: ...Engine Off 17 Setting Adjustable Rocker Arms 18 Adjusting Clearance on Overhead Camshaft Engines 18 Setting Valve Lash with Replaceable Shims 18 CAMSHAFT AND VALVE TIMING 19 Variable Valve Timing 19 C...

Страница 119: ...LS 56 Mechanical Fuel Pump Testing 57 Pressure Test 57 Volume Test 57 Electric Fuel Pump Testing 57 Fuel Injection Testing 57 Relieving Fuel Pressure 58 Fuel Injection Pressure Test 58 Fuel Injection...

Страница 120: ...ng Open Loop and Closed Loop Operation 92 Driveability Symptom Tests 92 Computer Controlled Timing Service 93 Operating Range Tests 93 Road Test and Record Data 93 Diagnosis Of Emissions And Drivabili...

Страница 121: ...the week before the test and again on the day of the test Arrive at the test site early so parking or unforeseen prob lems do not cause you stress Plan to allow time for a last look at your notes bef...

Страница 122: ...e ohmmeter lead to either coil primary terminal and touch the other ohm meter lead to the metal case of the coil Who is right a A only b B only c Both A and B d Neither A nor B 14 To check total centr...

Страница 123: ...ulation EGR system does all of the follow ing EXCEPT a Reduce oxides of nitrogen emis sions b Slow down the combustion process c Dilute the fuel mixture d Raise peak combustion temper atures 29 An air...

Страница 124: ...oscillations in the inter mediate section b An erratic jumping of the trace on the screen c A high firing peak and short sparkline in the firing section d Different firing spike heights be tween cyli...

Страница 125: ...B says a potentionmeter is a sensor that measures resist ance changes in proportion to tem perature Who is right a A only b B only c Both A and B d Neither A nor B 57 The purpose of the fuel pressure...

Страница 126: ...rless colorless tasteless poisonous gas A major pollutant from an internal combus tion engine Catalyst Specific compounds that enhance a chemical reaction without being consumed by the reaction Centri...

Страница 127: ...ery time the powertrain control module checks that circuit or function Hertz Hz A unit of frequency measurement equal to one cycle per second High Impedance A high level of opposition to current cre a...

Страница 128: ...aded pin and internal pressure to seal a port Sensor A device that provides an electric signal to a com puter to indicate a certain physical condition In an automo tive electronic system sensors monit...

Страница 129: ...The measurement of the loss of voltage caused by the resistance of a conductor or a circuit device Voltmeter A voltmeter is an instrument used for measur ing the potential difference or voltage betwee...

Страница 130: ...5 a 6 c 7 d 8 d Chapter E 1 b 2 a 3 c 4 a 5 b 6 d 7 a 8 c 9 b 10 b 11 b 12 b 13 c Sample Test 1 b 2 a 3 d 4 b 5 b 6 a 7 c 8 d 9 c 10 b 11 a 12 b 13 c 14 c 15 a 16 c 17 c 18 c 19 a 20 c 21 d 22 a 23 c...

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