Engine Performance (A8) The following report shows all assessment questions, indicates if the answer you provided was correct or incorrect, and reveals the correct answer. - Correct - Incorrect - Unanswered 1) Technician A says that some resistance in the power distribution circuits may harm the ignition switch or starter due to low voltage. Technician B says the power to the ignition switch is never fused. Who is correct? Incorrect A only Incorrect B only Incorrect Both A and B Correct Neither A nor B Question Rationale Answer A is incorrect. Low voltage will not harm the ignition switch or starter. Answer B is incorrect. Power to the ignition switch is fused. Answer C is incorrect. Neither Technician is correct. Answer D is correct. Neither Technician is correct. Low voltage will not harm the ignition switch or starter. Power to the ignition switch is fused. 2) Which of the follow diagnostic trouble codes are priority codes and should be troubleshooted first? Incorrect Transmission Incorrect Vehicle speed control Correct Misfire control Incorrect Emission controls Question Rationale Answer A is incorrect. Transmission codes are not high-priority codes. Answer B is incorrect. Vehicle speed control codes are not the highest priority codes listed. Answer C is correct. When a misfire occurs, the catalytic converter can be damaged, so misfire codes are of the highest priority and should be diagnosed first. Answer D is incorrect. Emissions-related codes will turn on the malfunction indicator lamp (MIL), but they are not the highest priority codes listed. 3) A charging system fuse link is being replaced. Technician A says the new fuse link should be soldered in place. Technician B says the new fuse link should be one size larger than the original to prevent it from burning again. Who is correct? Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. Fuse links should always be soldered in place to help resist corrosion. Answer B is incorrect. The replacement fuse link should be the same size as the original. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct. 4) A computer ground circuit should have no more voltage drop than: Correct 0.05 volt. Incorrect 0.5 volt. Incorrect 0.1 volt. Incorrect 1.0 volt. Question Rationale Answer A is correct. A computer ground should have no more than a 0.05-volt voltage drop. Answer B is incorrect. A computer ground should have no more than a 0.05-volt voltage drop. Answer C is incorrect. A computer ground should have no more than a 0.05-volt voltage drop. Answer D is incorrect. A computer ground should have no more than a 0.05-volt voltage drop. 5) A scan test of the computer system on a late-model fuel-injected engine reveals a bank 1 long-term fuel trim value of positive 22 and a bank 2 long-term fuel trim value of negative 2 with the engine idling. Technician A says these readings could be caused by a vacuum leak. Technician B says a bad oxygen sensor on bank 1 could cause these readings. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. A vacuum leak or a bad oxygen sensor can cause abnormal fuel trim corrections at idle. Answer D is incorrect. Both Technicians are correct. 6) All of the following conditions can cause high current readings during a starter current draw test EXCEPT: Incorrect shorted armature windings. Incorrect overadvanced ignition timing. Correct corroded battery cables. Incorrect insufficient crankshaft bearing clearances. Question Rationale Answer A is incorrect. Shorted armature windings will cause high current draw. Answer B is incorrect. Overadvanced ignition timing will cause high current draw. Answer C is correct. Corroded battery cables will increase resistance and cause lower current draw. Answer D is incorrect. Tight engine bearings will cause high current draw. 7) A battery is being load tested. Technician A says the voltage should be above 9.5 volts after 15 seconds of load is applied. Technician B says the load applied should be four times the cold cranking amps of the battery. Who is correct? Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. The battery should have at least 9.6 volts after a 15-second load test. Any voltage below 9.6 volts would not be sufficient to power up the electronics correctly. Answer B is incorrect. The battery should load test at 50 percent of its cold cranking amps, not four times the cold cranking amps. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct. 8) If the vacuum drops slowly to a low reading when a vacuum gauge is connected to the intake manifold and the engine is accelerated and held at a steady speed, it indicates: Incorrect sticking valves. Incorrect overadvanced ignition timing. Correct a restricted exhaust. Incorrect a rich fuel mixture. Question Rationale Answer A is incorrect. Sticking valves would not make the vacuum gauge drop. Answer B is incorrect. Advanced ignition timing would not cause vacuum to decrease. Answer C is correct. An exhaust restriction reduces airflow through the engine and will increase intake manifold pressure, which reduces the vacuum reading. Answer D is incorrect. Rich fuel mixtures would not cause a vacuum decrease off idle. 9) Technician A says a voltage drop test checks the amount of resistance between two test points. Technician B says more than a 0.5-volt voltage drop indicates excessive resistance across the positive battery cable. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. A voltage drop test is a more accurate way of finding resistance in a circuit than using an ohmmeter. Voltage drop is defined as the voltage used pushing current through a resistance. A battery cable should pose very little resistance to current flow, so performing a voltage drop test across the cable determines if excessive resistance is present in the cable. A voltage drop greater than 0.5 volt across a positive battery cable is excessive. Answer D is incorrect. Both Technicians are correct. 10) A vehicle emits a belt squeal when starting and on acceleration. Technician A says the alternator bearings may be defective. Technician B says the alternator belt automatic tensioner may be defective. Who is correct? Incorrect A only Correct B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. A defective bearing would make noise all the time, not just at startup and acceleration. Answer B is correct. Only Technician B is correct. If the tensioner fails to keep the belt tight, the belt could squeal on startup and acceleration. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Technician B is correct. 11) A charging system has no charging system output. Technician A says the powertrain control module might be the cause. Technician B says the integrity of the charging system wiring should be checked before any components are replaced. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. On some vehicles, the PCM controls the field circuit of the alternator. The lack of alternator output could be caused by an open circuit in the field circuit as well. The integrity of the wiring in the system should be checked before any components are replaced. Answer D is incorrect. Both Technicians are correct. 12) Technician A says the engine should be disabled to prevent engine startup during a starter current draw test. Technician B says some vehicles can be held to the floor on the accelerator to prevent starting during a current draw test. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. When performing a starter current draw test, the engine must be disabled to prevent starting. Some vehicles have a clear flood mode that disables the injectors when held to the floor. Answer D is incorrect. Both Technicians are correct. 13) During engine testing, a technician observes tailpipe CO readings that are higher than normal at idle. Which of these is the most likely cause? Incorrect Constant high oxygen sensor signal voltage Incorrect An EGR valve not seating Incorrect A bad ignition module Correct An EVAP purge solenoid stuck open Question Rationale Answer A is incorrect. A constant high oxygen sensor signal voltage is the result of a rich air/fuel mixture, and not the cause. The computer should lean out the air/fuel mixture in response to the high O2 signal voltage, and this would cause lower CO emissions. Answer B is incorrect. An EGR valve not seating would dilute the incoming mixture at idle and cause a misfire and rough idle. The misfire would cause increased hydrocarbons and lower CO because combustion does not take place properly with a misfire. Answer C is incorrect. A bad ignition module would not cause an increase in CO emissions. It would be more likely to cause a misfire and increased hydrocarbons. Answer D is correct. A stuck-open purge solenoid could allow fuel vapors to be drawn into the engine during idle, enriching the air/fuel mixture and increasing CO emissions. 14) During a cylinder leakdown test on a 4-cylinder engine, air is heard coming from spark plug hole 3 as cylinder 4 is being checked. Technician A says that this could be caused by a blown head gasket. Technician B says this could be caused by a cracked engine block. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. If there is a leak in an adjacent cylinder, look at what is “common” to both cylinders. Answer D is incorrect. Both Technicians are correct. 15) The alternator belt and belt tension are satisfactory, but the alternator output is low. Technician A says the alternator voltage regulator may be the cause. Technician B says the problem could be high resistance in the alternator field circuit. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. A defective voltage regulator or high resistance in the field could both cause low alternator output. Answer D is incorrect. Both Technicians are correct. 16) When performing a starter current draw test, high current draw can be caused by all of the following EXCEPT: Incorrect high resistance. Correct overcharged battery. Incorrect engine problems. Incorrect shorted field coils in the starter. Question Rationale Answer A is incorrect. High resistance in the starter circuit would cause high current draw during a starter current draw test. Answer B is correct. A battery with a high state of charge would not cause the starter to have high current draw. Answer C is incorrect. Engine problems, such as seizing bearings, would cause high current draw. Answer D is incorrect. Shorted field windings in the starter coil would cause high current draw. 17) Technician A says valve adjustment should always be performed on a cold engine. Technician B says the piston should be placed at TDC of the compression stroke. Who is correct? Incorrect A only Correct B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Not all valve adjustments require the engine to be cold. Some manufacturers specify a warm engine. Answer B is correct. Only Technician B is correct. Many adjustment procedures require the piston at top dead center on the compression stroke as the intake and exhaust valves are closed. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Technician B is correct. 18) The vacuum gauge in the figure indicates low vacuum. Technician A says late ignition timing will cause a low vacuum reading. Technician B says to connect the gauge to a ported vacuum port. Who is correct? Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. Retarded ignition timing will cause peak combustion pressure to occur too late in the power stroke. This reduces crankshaft velocity and rpm and causes low intake manifold vacuum. Answer B is incorrect. Connecting the vacuum gauge to a ported vacuum source will read vacuum off idle when the throttle is opened, not at idle. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct. 19) A vehicle with a hard-to-start complaint is being diagnosed. The battery shows an open circuit voltage of 11.5 volts. Technician A says the battery should be recharged then load tested. Technician B says the battery cranking voltage also should be checked. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. An open circuit voltage of 11.5 volts is too low, and the battery should be recharged then load tested. Another test that could be done is a cranking voltage test. Answer D is incorrect. Both Technicians are correct. 20) A vehicle emits a belt squeal when starting and on acceleration. Technician A says the alternator bearings may be defective. Technician B says that the alternator belt may be loose. Who is correct? Incorrect A only Correct B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. A squeal is an indication of a loose belt. Defective bearings make a growl noise. Answer B is correct. Only Technician B is correct. A loose alternator belt will cause the vehicle to emit a belt squeal when starting and on acceleration. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Technician B is correct. 21) Technician A says a scan tool is required to retrieve trouble codes. Technician B says OBD-II compliant vehicles use a standardized trouble code format. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. OBD-II vehicles require a scan tool to retrieve trouble codes; flash codes are no longer supported. OBD-II regulations require the use of standardized diagnostic trouble code formats. Answer D is incorrect. Both Technicians are correct. 22) Technician A says the EGR system is used to lower combustion chamber temperature. Technician B says that EGR systems that use an EGR valve position sensor should read about 4.5 volts with the EGR valve at full open. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. The EGR system is used to control oxides of nitrogen. It does this by lowering the combustion chamber temperature. If the EGR system uses an EGR position sensor, it will read about 4.5 volts with the valve at full open. Answer D is incorrect. Both Technicians are correct. 23) A vehicle with an SFI V6 engine and OBD-II emissions controls has set a DTCPO171 (system too lean, bank 1). No other driveability concerns are present. The freeze frame data shows the code was set under warm idle conditions. Technician A says the problem could be an intake manifold vacuum leak. Technician B says the problems could be a weak fuel pump. Who is correct? Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. A vacuum leak can set a fuel trim trouble code with no other driveability problems present. Answer B is incorrect. A weak fuel pump would not cause problems at idle when fuel demand is low. Other driveability problems like lack of power would be present. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct. 24) An engine has a lack of power and excessive fuel consumption. Technician A says a broken timing belt cannot be the cause. Technician B says the timing belt may have jumped a tooth. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. If the timing belt were broken, the engine would not run. A jumped tooth on the timing belt would change valve timing and volumetric efficiency. Answer D is incorrect. Both Technicians are correct 25) A technician connects a jumper wire between the alternator B and F terminals during a field circuit and alternator test. Technician A says if this corrects a low-voltage reading, the wiring harness from the alternator to the regulator could be faulty. Technician B says this bypasses the voltage regulator. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. This excites the field, causing the alternator to produce near full output. This is basically used as a “process of elimination” when diagnosing charging systems, as it separates the alternator and regulator circuits. Answer D is incorrect. Both Technicians are correct. 26) A vehicle is hard to start due to low cranking speed. A starter draw test reveals excessive current draw from the starter. Technician A says the battery cables should be voltage drop tested to determine if there is excessive resistance. Technician B says the starter motor armature may be dragging on the field coils. Who is correct? Incorrect A only Correct B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. The relationship of voltage, amperage, and resistance states that excessive amperage and resistance cannot be present at the same time. High resistance in the battery cables will not cause high current draw from the starter motor. Answer B is correct. Only Technician B is correct. A dragging armature will cause increased current flow in a starter motor and lower cranking speeds. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Technician B is correct. 27) A vehicle is being diagnosed for a PO134 trouble code (oxygen sensor circuit, no activity detected on bank 1, sensor 1). Technician A says the problem could be low fuel system pressure. Technician B says the problem is more likely confined to the downstream oxygen sensor on the bank where the number 1 cylinder is. Who is correct? Incorrect A only Incorrect B only Incorrect Both A and B Correct Neither A nor B Question Rationale Answer A is incorrect. Low fuel pressure would affect all sensor readings, not just one. Answer B is incorrect. Bank 1, sensor 1 is the upstream sensor on the bank that number 1 is on. Answer C is incorrect. Neither Technician is correct. Answer D is correct. Neither Technician is correct. Low fuel pressure would affect all sensor readings, not just one. Bank 1, sensor 1 is the upstream sensor on the bank that number 1 is on. 28) Technician A says that if some EGR passages are plugged in the intake manifold, the engine may misfire when the EGR valve opens due to excessive EGR flow to the remaining cylinders. Technician B says that plugged EGR passages may cause a failed IM240 emissions test for high oxides of nitrogen. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. If the EGR passages to only one or two cylinders are plugged in the intake manifold, the other cylinders will receive excessive exhaust gas flow when the EGR valve opens and have a density misfire problem. Plugged EGR passages will also raise NOx levels and can result in an IM240 emissions test failure. Answer D is incorrect. Both Technicians are correct. 29) Technician A says because of extreme temperatures in the exhaust stream, restricted EGR passages are not a problem. Technician B says that before any EGR parts are replaced, all passages should be clean. Who is correct? Incorrect A only Correct B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Restricted passages are always a problem in the exhaust. Answer B is correct. Only Technician B is correct. All passages should be clean before any EGR parts are replaced. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Technician B is correct. 30) All of the following checks are correct for testing the coolant sensor and/or circuitry EXCEPT: Incorrect resistance and voltage checks. Incorrect DTCs and scan data. Incorrect thermometer, heated water, and resistance check. Correct diode check. Question Rationale Answer A is incorrect. Resistance and voltage checks are an approved method for checking coolant sensors. Answer B is incorrect. A scan tool can be used to view the data on the coolant sensor as well as to read any DTCs. Answer C is incorrect. The coolant temperature sensor can be placed in heated water while the resistance is measured. Answer D is correct. A diode check would not be used to test the coolant sensor and/or circuitry. 31) Technician A says the PCM will increase the fuel injector pulse width if there is excess oxygen in the exhaust. Technician B says if there is a lean condition, the SFT will show a minus value on the scan tool. Who is correct? Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. The pulse width increases to richen the mixture. Answer B is incorrect. Short-term fuel is subtracted or reduced as a result of a rich condition. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct. 32) While testing a pulse air-injection system, Technician A says with the air cleaner clean air hose removed and the engine idling, there should be steady audible pulses at the end of the hose. Technician B says air pulses should be felt escaping through the clean air hose on some vehicles. Who is correct? Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. Audible pulses of air are an indication of air being drawn into the exhaust system. Answer B is incorrect. Air pulses felt escaping through the fresh air inlet indicate broken or leaking reed valves in the pulse-air system. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct. 33) Technician A says if you are testing an ignition-related no-start problem, you should always check for available spark at an ignition wire first. Technician B says if you have a test light connected to the negative side of the coil while cranking and the test light flickers, you need to test the secondary ignition system. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. The first step in diagnosing a no-start condition in which the ignition system is suspected is to test for available spark at a spark plug wire. A test light connected to the negative side of an ignition coil that flickers or blinks indicates the primary side ignition components are functioning and the secondary ignition components should be tested next. Answer D is incorrect. Both Technicians are correct. 34) A scan tool is being used in addition to a thermometer to check thermostat operation. Technician A says using both tools will aid in making an accurate diagnosis of thermostat operation. Technician B says thermostat operation can also be checked visually by running the engine until it is hot. Who is correct? Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. The thermostat opening temperature can be monitored on the scan tool and cross-checked with the thermometer. Answer B is incorrect. Accurate operation of the thermostat cannot be checked visually while installed. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct . 35) A vehicle with an under-car rattle and low engine power is being diagnosed. Technician A says an exhaust back pressure test should be performed. Technician B says the catalytic converter may have come apart and may be restricting exhaust flow. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. The exhaust back pressure should be measured. The exhaust system rattle could be caused by loose components in the catalytic converter causing a restricted exhaust flow. A restriction in the exhaust can cause a loss of power on acceleration and cruise. Answer D is incorrect. Both Technicians are correct. 36) All of the following are true of the cylinder leakage test EXCEPT: Incorrect air loss and bubbles in the radiator indicate a bad head gasket or engine casting crack. Incorrect air loss from the oil filler cap indicates worn piston rings. Correct a gauge reading of 100 percent indicates no cylinder leakage. Incorrect air loss from the exhaust indicates a valve problem. Question Rationale Answer A is incorrect. Air loss and bubbles in the radiator indicate a blown head gasket or cracked head or block casting. Answer B is incorrect. Air escaping from the crankcase could indicate problems with the rings. Answer C is correct. A reading of 100 percent indicates a major, total cylinder leak, either due to an incorrect crank position (valve open) or internal damage. A reading of up to 20 percent is considered normal. Answer D is incorrect. Air escaping from the exhaust indicates a bad exhaust valve. 37) A stuck air-injection control valve that constantly sends air pump output to the exhaust manifold will most likely result in: Incorrect improved fuel economy. Incorrect pinging on acceleration. Incorrect engine overheating. Correct a constant lean oxygen sensor signal. Question Rationale Answer A is incorrect. Air pump output constantly directed to the exhaust manifold will most likely decrease fuel economy because the computer will see a lean exhaust signal and increase fuel delivery. Answer B is incorrect. Air injected into the exhaust manifold would not cause pinging on acceleration. Answer C is incorrect. Air injected into the exhaust manifold constantly would not cause engine overheating. Answer D is correct. Air injected into the exhaust manifold constantly will cause the oxygen sensor to send a continuous lean output or low-voltage signal. 38) While monitoring secondary ignition with an oscilloscope, as shown in the figure, the LEAST LIKELY cause of high resistance in the ignition secondary circuit is: Incorrect damaged spark plug wires. Correct no dielectric compound on the ignition module mounting surface. Incorrect corroded spark plug wire ends. Incorrect excessive spark plug air gap. Question Rationale Answer A is incorrect. Damaged carbon ignition wires cause high resistance. Answer B is correct. The ignition module is common to all cylinders and is part of the primary ignition circuit. Answer C is incorrect. Corroded spark plug wire ends will cause high resistance. Answer D is incorrect. An excessive spark plug gap causes high resistance. 39) Technician A says that the first step of any diagnostic procedure is to check for diagnostic trouble codes (DTCs). Technician B says that the customer complaint should be verified before performing any diagnostic procedures. Who is correct? Incorrect A only Correct B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. The first step in a diagnostic procedure should be to verify the customer concern. Only if a concern is related to a system that has self-diagnostic capabilities does it make sense to check for trouble codes. Answer B is correct. Only Technician B is correct. If a customer complaint cannot be verified, then diagnostic testing may not produce any results. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Technician B is correct. 40) Low battery or system voltage can cause all of the following EXCEPT: Incorrect increased ignition dwell. Incorrect increased injector on-time. Incorrect increased idle speed. Correct increased steering effort. Question Rationale Answer A is incorrect. Ignition dwell can increase to fully saturate the coil when system voltage is low. Answer B is incorrect. Injector on-time can increase to maintain the proper air/fuel mixture due to slower injector opening when system voltage drops. Answer C is incorrect. The idle speed can increase to help drive the alternator faster at idle speed. Answer D is correct. Low-system voltage cannot reduce steering effort. 41) Technician A says to prevent backfiring during deceleration on pump-driven air-injection systems, a diverter valve is used. Technician B says to prevent exhaust gases from back flowing into the air-injection control valves or pump, check valves are used in the exhaust manifold and converter feed pipes. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. Air-injection diverter valves prevent backfiring during deceleration by redirecting air pump output to atmosphere. Air-injection check valves allow airflow in only one direction, preventing exhaust from backing up into the air-injection system. Answer D is incorrect. Both Technicians are correct. 42) Referring to the figure, Technician A says a deteriorated belt could cause squealing and chirping. Technician B says belt deflection should be under 1/2 inch (12.7 mm) per foot (30.5 cm) free span. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. Glazed, cracked, or deteriorated belts can make noise. The proper fix is to replace the belt. In any case, the proper belt tension adjustment must be made. Answer D is incorrect. Both Technicians are correct. 43) Technician A says that during a powertrain control module replacement, the technician should use a grounding strap to prevent static charge from damaging the PCM. Technician B says care should be taken not to touch the PCM terminals with your fingers. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. A defective starter drive or a defective starter solenoid can cause a whining noise. Answer D is incorrect. Both Technicians are correct. 44) When testing a viscous-drive fan clutch, as shown in the figure, with the engine off, rotate the cooling fan by hand. It should have: Correct more resistance hot. Incorrect more resistance cold. Incorrect no rotation movement. Incorrect no resistance. Question Rationale Answer A is correct. Hotter temperatures result in more resistance, thus causing the fan to move more air across the radiator. Answer B is incorrect. It has less resistance cold, when fan-blown air is not needed, to improve performance and fuel economy. Answer C is incorrect. It should have movement. Answer D is incorrect. The clutch should have resistance. 45) Technician A says oil found inside the air filter housing may be caused by a plugged or restricted PCV valve or hose. Technician B says a plugged PCV valve will cause excessive crankcase blowby. Who is correct? Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. A plugged or restricted PCV valve or hose will cause crankcase pressure to rise and force oil vapors into the air filter housing. Answer B is incorrect. Excessive crankcase blowby is caused by internal engine wear. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct. 46) A cylinder power balance test can indicate all of the following problems EXCEPT: Incorrect a bad spark plug. Correct late ignition timing. Incorrect an open ignition wire. Incorrect burned valves. Question Rationale Answer A is incorrect. Defective spark plugs can be diagnosed with a cylinder balance test. Answer B is correct. Timing is common to all cylinders. Answer C is incorrect. Faulty ignition wires can be determined with cylinder power balance tests. Answer D is incorrect. Burned valves can be diagnosed with cylinder power balance tests. 47) All of the following are used to check the oxygen sensor EXCEPT a: Incorrect high-impedance voltage meter. Correct low-impedance voltage meter. Incorrect lab scope. Incorrect graphing meter. Question Rationale Answer A is incorrect. A meter with high impedance is safe to use on the computer control system and sensors. Answer B is correct. A meter with low impedance draws too much current and can damage the computer control system and give inaccurate readings. Answer C is incorrect. A lab scope is used to see the oxygen sensor switching signal. Answer D is incorrect. A graphing meter is used to see the oxygen sensor signal. 48) Technician A says that when vacuum is applied to the exhaust gas recirculation (EGR) valve with the engine idling, the EGR valve should open and idle should become erratic. Technician B says that a diagnosis of the EGR valve should not be done with the engine idling. Who is correct? Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. Introducing EGR gases into the engine at idle will cause severe idle roughness or stall the engine. Answer B is incorrect. It is best to determine if EGR gases are reaching the combustion chamber by opening the EGR valve during engine idle because higher rpm conditions might not show a change when the EGR valve is opened. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct. 49) A vehicle with a rich exhaust code is being diagnosed. Technician A says the fuel pressure could be the cause. Technician B says a ruptured fuel-pressure regulator diaphragm could be the cause. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. Either a high fuel pressure or a ruptured diaphragm in a fuel-pressure regulator could cause a rich exhaust code. Answer D is incorrect. Both Technicians are correct. 50) The vanes on a turbocharger compressor wheel are severely pitted. The cause of this problem could be: Incorrect partially seized turbocharger bearings. Incorrect excessive turbocharger shaft end play. Correct a leak in the air intake system. Incorrect an overheated turbocharger. Question Rationale Answer A is incorrect. Pitting cannot be caused by the bearings. Answer B is incorrect. Excessive end play would damage only the bearings. Answer C is correct. A leak in the air intake system could cause the vanes to become severely pitted. Answer D is incorrect. An overheated turbocharger would affect only the bearings. 51) Technician A says if the exhaust gas recirculation (EGR) valve remains open at idle and low speed, the idle will be rough. Technician B says if the EGR valve does not open, detonation can occur. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. A stuck-open EGR valve causes diluted air/fuel mixture, while an EGR system that does not operate causes high combustion chamber temperatures, resulting in detonation and NOX output. Answer D is incorrect. Both Technicians are correct. 52) The LEAST LIKELY cause of spark knock is: Incorrect EGR valve stuck closed. Incorrect fuel quality. Incorrect carbon buildup on top of the pistons. Correct EGR valve stuck open. Question Rationale Answer A is incorrect. A stuck-closed EGR valve can cause spark knock. Answer B is incorrect. Poor fuel quality can cause spark knock. Answer C is incorrect. Carbon buildup in the combustion chamber can cause spark knock. Answer D is correct. A stuck-open EGR valve would not cause spark knock. Other driveability problems would be present. 53) All of the following apply to OBD-II guidelines EXCEPT: Incorrect use of a standard list of diagnostic trouble codes. Incorrect standard communication protocol. Incorrect ability to record and store fault conditions when they occur. Correct turn on the MIL if emission levels exceed four times the standards for that model year vehicle. Question Rationale Answer A is incorrect. This is an OBD-II standard. Answer B is incorrect. This is an OBD-II standard. Answer C is incorrect. This is an OBD-II standard. Answer D is correct. The threshold amount is 1.5 times the limit, not 4. 54) When installing and timing the distributor, Technician A says the engine must be timed referencing TDC on the specified cylinders exhaust stroke. Technician B says if the engine is timed on the compression stroke, the distributor will be 180 degrees off. Who is correct? Incorrect A only Incorrect B only Incorrect Both A and B Correct Neither A nor B Question Rationale Answer A is incorrect. Most engines will require spark delivery to occur several degrees before the piston reaches top dead center of the compression stroke. Answer B is incorrect. The engine should be timed with the engine on the compression stroke. Answer C is incorrect. Neither Technician is correct. Answer D is correct. Neither Technician is correct. The distributor is timed to the number one cylinder on the compression stroke. 55) Technician A says that if the measurement in the figure is set too wide, it will retard valve timing. Technician B says it will reduce valve overlap. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. The valve will open late and close early, reducing flow and overlap. Answer D is incorrect. Both Technicians are correct. 56) All of the following symptoms are true of low fuel pressure EXCEPT: Correct excessive sulfur smell. Incorrect lack of power. Incorrect engine surging. Incorrect limited top speed. Question Rationale Answer A is correct. Sulfur odor is usually from a rich condition. Answer B is incorrect. Lack of power is a symptom of low fuel pressure. Answer C is incorrect. Engine surging is a symptom of low fuel pressure. Answer D is incorrect. Limited top speed is a symptom of low fuel pressure. 57) A vehicle with a suspected undercharging problem is being diagnosed. Technician A says the charging system voltage at idle should be at least 13.5 to 14.5 volts. Technician B says the charging system voltage at 2,000 rpm should be at least 12.5 to 13.5 volts. Correct A only Incorrect B only Incorrect Both A and B Incorrect Neither A nor B Question Rationale Answer A is correct. Only Technician A is correct. Charging system voltage at idle should be 13.5 to 14.5 volts. Answer B is incorrect. Charging system voltage at 2,000 rpm should be at least 13.5 to 14.5 volts and will usually be higher than idle voltage. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Technician A is correct. 58) An EGR vacuum regulator solenoid (EGRV) is thought to be inoperative. Technician A says when an ohmmeter is connected, as shown in the figure, a lower-than-specified reading means the windings are open. Technician B says an infinite reading means the winding is shorted. Who is correct? Incorrect A only Incorrect B only Incorrect Both A and B Correct Neither A nor B Question Rationale Answer A is incorrect. An infinite reading indicates only an open winding. Answer B is incorrect. An infinite reading does not indicate a shorted winding. Answer C is incorrect. Neither Technician is correct. Answer D is correct. Neither Technician is correct. An infinite reading indicates only an open winding; it does not indicate a shorted winding. 59) A vehicle is equipped with a vented gas cap. Technician A says if a nonvented cap is installed in this vehicle, the gas tank could collapse. Technician B says that if a nonvented cap is installed, the vehicle could be starved for fuel at high speeds. Who is correct? Incorrect A only Incorrect B only Correct Both A and B Incorrect Neither A nor B Question Rationale Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer C is correct. Both Technicians are correct. The gas cap is an integral part of the design of the fuel and emission control system, and calibrated for the application. Internal fuel tank pressures can be affected by the use of an improper or faulty cap. Answer D is incorrect. Both Technicians are correct. 60) If the air/fuel mixture is ignited before the spark plug fires, this is called: Correct preignition. Incorrect overadvanced timing. Incorrect dieseling. Incorrect lean burn combustion. Question Rationale Answer A is correct. Combustion beginning before the timed spark is called preignition. Answer B is incorrect. Overadvanced timing should not start combustion. Answer C is incorrect. Dieseling is the after run that occurs in a gasoline engine when air and fuel are ignited in the combustion chamber by hot spots after the engine is turned off. Answer D is incorrect. Lean burn combustion is a technology, not an abnormal combustion event. © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
Posted on: Wed, 30 Oct 2013 16:25:23 +0000
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