FINAL EXAM - AUMT 2435: ENGINE PERF. ANANLYSIS 11
NAME
Grade Circle the letter next to the most correct answer.
1. A 4-year old pickup truck has a high CO reading. Technician A says that a hole in the exhaust
downstream from the oxygen sensor could be the cause. Technician B says a defective (electrically open)
injector could be the cause. Which technician is correct?
a. Technician A only
b. Technician B only
c. Both Technician As and B
d. Neither Technician A nor B
2.
A vehicle that has a higher than normal HC and CO reading is most likely running:
a. Rich
b. Lean
3. A customer comments that the engine misses when going up a hill or on hard acceleration. When
viewing the scope, the technician sees that the #5 firing line is about 5 to 6 kV higher than the rest, and
the spark line slants down from the firing line to the coil oscillations. What is the most likely cause?
a. A fuel fouled plug on #5
b. A plug with a wom electrode on #5
c. A high resistance plug wire on #5
d. This is a normal pattcm
4. On a cylinder balance test, all cylinders should be within RPM of each other.
a. 10
b. 50
c. 150
d. 500
5. Pinging can be caused by:
a. Retarded ignition timing
b. Advanced ignition timing
6. What is the most likely cause of a spark line sloping up toward the coil oscillations?
a. A lean air/fuel mixture
b. An open plug wire
c. A wide plug gap
d. A narrow plug gap
7.
A high 02S voltage could be due to:
a. A rich exhaust
b. A lean exhaust
c. A defective spark plug wire
d. Both a and c
8. A low 02S voltage could be due to:
a. A rich exhaust
b. A lean exhaust
c. A defective spark plug wire
d. Both b and c
9. A fuel-injected vehicle is tested on a 4-gas exhaust analyzer.
HC = 102 PPM CO ~ 0.3% 02 ~ 6.3% C02 = 6.1%
Technician A says that everything is OK including the TP setting because the 02 and C02 are
about equal. Technician B says that the engine is running lean. Which technician is correct?
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
10. A broken valve spring could be indicated best by which test?
a. Running compression; cranking vacuum
b. Running compression; running vacuum
c. Cranking compression; cranking vacuum
d. Scope firing lines; cranking vacuum
11. A vacuum leak could be indicated best by which test?
a. Compression test (cranking)
b. Idle vacuum test
c. Vacuum at 2,000 R-PM
d. Spraying carburetor cleaner
12. A clogged exhaust system could be best indicated by which test?
a. Vacuum test at idle
b. Vacuum at 2,000 RPM
c. Cylinder leak down rate
d. Running compression test
13. Retarded valve timing would best be indicated by:
a. A high steady vacuum (idle)
b. A low steady vacuum (idle)
c. Low leakage, high compression
d. Low compression, low leakage
14. A technician is working on a vehicle equipped with a port-injected engine. After connecting the
vehicle to a scan tool, the technician finds it has a long ten-n fuel trim of 150. Technician A says that an
exhaust leak in front of the oxygen sensor could cause this. Technician B says that a defective plug wire
could cause this. Which technician is correct?
a. Technician A only
b. Techrilcian B only
c. Both Technicians A and B
d. Neither Technician A nor B
15. A short-terin fuel trim of 126 and a long-ten-n fuel trim of 155 means:
a. The engine is running lean now
b. The engine has a history of running rich
c. The engine has a history of running lean
d. The engine is running rich now
16. A tracked ignition coil will:
a.
b.
c.
d.
Measure as shorted with an ohmmeter
May indicate continuity with an ohmmeter between the primary or secondary
windings to the metal laminations
Miss under load
Miss at cruise
17. A vehicle equipped with TBI has exhaust gas readings of.
HC = 380 PPM
CO= 0-01%
a. The catalytic converter is not working
b. The fuel pressure regulator is defective
c. The thermostat is too cold
d. The IAC is too high
I S. The catalytic converter can be tested using:
a. A vacuum gauge connected to the intake manifold vacuum
b. Temperature measuring tool
c. A pressure gauge attached in the place of the 02S
d. All of the above
C02 = 14.7%
02 = 1%
19, A four-cylinder TBI engine has a rich DTC. Technician A says that this could be caused by a faulty
injector. Technician B says a faulty MAP sensor could be the cause. Which technician is correct?
a.
b.
c.
d.
Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
20. 02S bias voltage:
a. Is the average of the high and low 02S voltage during the last 1.25 seconds
b. Is the voltage the ECM applies to the 02S
c. Is the voltage the 02S applies to the ECM during open loop
d. Is the static electricity charge voltage that builds up on the 02S during closed loop
operation
21. The oil pressure warning light comes on at:
a. I psi
b. 4 psi
C. 8 psi
d. 12 psi
22. A 4-cylinder engine with electronic ignition (distributorless) has no injector pulse or spark available
when the engine is cranked. The problem is most likely a faulty:
a. Cam sensor
b. ECM
c. Crank sensor
d. Ignition module
23. A proper operating fuel-injected engine should develop 02S cross counts at
2000 RPM.
a. 200 to 800
b. I to 3
c. The higher the better - minimum of 8
d. The lower the better - maximum of 41
24. A vehicle falls the paper test. (A piece of paper held near the tailpipe fluctuated rapidly.) A possible
cause could be:
a. A defective fuel injector
b. A defective spark plug wire
c. c. A burned valve
d. d. All of the above
25.
An idling fuel-injected engine shows an IAC count of 2. This means:
a. A non-nal reading
b. The engine could have a vacuum leak
c. The engine oil is too thick
d. There is a defective JAC
26. A GM fuel-injected engine has a long term fuel trim of 152 at idle and a long term fuel trim of 128 at
2000 RPM. The most like~y cause is:
a. A small vacuum leak
b. A defective MAF
c. A defective fuel pressure regulator
d. A faulty JAC
27. An engine will not start. A technician unplugs the MAF sensor and the engine starts. The most likely
cause of the no-start condition was:
a. A defective PROM
b. A defective TP sensor
c. A defective MAF sensor
d. A defective MAP sensor
28. A small vacuum leak occurs at the end of the vacuum hose going to the MAP sensor. The most likely
result will be:
a. A lean code
b. A rich code
29. A fuel-injected engine hesitates on acceleration. Which sensor or system should the technician test
first?
a. The oxygen sensor
b. The cylinder compression
c. The TP sensor
d. The exhaust back pressure
30. The spark line is short in duration (.60mS maximum), and the firing line is low on all cylinders. What
is the most likely cause?
a. The cap to rotor button has excessive resistance
b. The rotor to distributor air gap is too close
c. The secondary is shorted between its windings
d. The primary coil resistance is too low
NOTE: Questions 31 through 35 are based on the secondary idle scope pattern shown.
31. Point "A" indicates that:
a. Dwell is beginning
b. The coil is being energized
c. The module transistor is turning off
d. The module transistor is turning on
32. Point "B" indicates:
a. The voltage required to ionize the spark plug gap
b. The total resistance to be overcome in the secondary circuit
c. The voltage required to maintain the spark
d. Botha and b
33. Area "C" would be affected by:
a. Spark plug gap
b. Spark plug resistance
c. Cap to rotor air gap
d. All of the above
34. Point "D" indicates the end of-.
a. The firing line
b. The spark line
c. Dwell
d. Module saturation
35. The downward line at point "F" indicates the:
a. Beginning of the intermediate section
b. Module transistor completing ground to the primary coil
c. Module turning OFF the primary coil current
d. End of the dwell section
36. A worn (stretched) timing chain would cause the engine to produce:
a. Low power with a rough idle b. Smooth idle, but the engine starts to miss at higher speeds c. Smooth
idle, but the engine lacks power at higher speeds d. Low power at low speed, okay at higher speeds
37. An engine has a rough idle condition. The technician checks the spark duration and obtains the
following results:
Cylinder #1 - .90 mS.
Cylinder #2 - 1.0 mS.
Cylinder #3 - 1.1 mS.
Cylinder #4 - 2.4 mS.
What is the most likely cause?
a. Cylinder #1 plug has a wide gap b. Cylinder #4 plug has a wide gap c. Cylinder #4 plug has a narrow
gap d. Cylinder #I plug has a narrow gap
38. Typical fuel pump pressure as measured on a running port-injected vehicle is usually.
a. 9 - 13 psi b. 20 - 30 psi c. 35 - 45 psi d. 70 - 90 psi
39. Typical fuel pump pressure as measured on a running throttle body fuel-injected vehicle is usually:
a. 9 - 13 psi b. 20 - 30 psi c. 35 - 45 psi d. 70 - 90 psi
40. On a V-6 engine equipped with electronic ignition (distributorless) with a firing order of 123456,
what is common about cylinders #6 and #3?
a. They share the same barrel of the TBI b. They share the same runner of the intake manifold c. They are
opposite each other in the engine d. They are paired cylinders
41. What is the most likely result of a cracked spark plug?
a.
b.
c.
d.
Miss at idle only - the extra fuel during acceleration will "cover up" or prevent the
miss above idle
Miss during acceleration and the engine will shake
The engine will run OK because the computer will compensate
The engine will run OK - maybe a little low on power
42. An engine starts, then stalls. If the 02S is removed, the engine will start and run. The most likely
cause is a:
a. Stuck open EGR valve b. Defective 02S c. Skewed MAP sensor d. Clogged exhaust system
43. Slow jerky cranking when hot and ping (detonation or spark knock) during acceleration are an
indication of:
a. Advanced ignition timing b. Retarded ignition timing
44. A higher than normal IAC count on an idling engine could be caused by a defective:
a. JAC b. 02 sensor c. TP sensor d. MAF or MAP sensor
45. Two technicians are discussing catalytic converters. Technician A says that a non-working catalytic
converter will test as being clogged during a vacuum or back pressure test. Technician B says that the
temperature of the inlet and outlet of the converter can detect if it is working okay. Which technician is
correct?
a. Technician A only b. Technician B only c. Both Technician A and B d. Neither Technicians A nor B
46. A 1994 vehicle is being tested on a 4-gas machine. HC = 714 PPM, CO = 4.14%, C02 7.41% and 02
= 6.72%. The most likely cause is:
a. A lean mixture with bad ignition wires b. A defective catalytic converter and a rich mixture c. A rich
mixture, a defective catalytic converter, and a hole in the exhaust d. A rich mixture and excessively
advanced ignition timing
47. An engine is not reaching proper operating temperature. The most likely result is:
a. Poor fuel economy
b. Pinging on acceleration
c. Low power
d. Dieseling when the ignition is turned off
48. A vacuum leak occurs when a small vacuum hose falls off on V-8 engine with port-fuel injection. The
owner then has the vehicle tested for exhaust emissions. The most likely result will be:
a. High HC and very low CO
b. Normal readings
c. Low 02 and CO
d. Low C02 and 02
49. An engine cranks, but will not start. Technician A says to check for spark using a ST-125.
Technician B says you can check to see if the injectors are being pulsed by using a nold light or logic
probe. Which technician is correct?
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
50. Oxygenated fuels reduce
emission.
a. HC
b. CO
C- C02
d. N 0,
5 1. A vehicle falls an enhanced exhaust emission test for NO, Technician A says that decarbonization
may help. Technician B says that the EGR passages should be cleaned. Which technician is correct?
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
52. HC and C02 are high and CO and 02 are low. The most likely cause is:
a. Too rich b. A fault in the secondary ignition system c. Stuck open EGR d. Lean misfire
53. A fuel pressure test indicates low fuel pump pressure on a port-injected vehicle. The technician
pinches off the fuel return line and the pump pressure reaches normal maximum pressure. This test
indicates:
a. The injectors are leaking down b. The regulator is defective c. The pump is defective d. The oil
pressure switch or fuel pump relay is defective
54. When a technician removes the vacuum hose from the fuel pressure regulator on a portinjected
engine, what should occur?
a. The engine should stumble or stall b. The fuel pressure should increase c. The fuel pressure should
decrease d. The engine will greatly increase in speed (RPM)
55. A defective oxygen sensor can fail "high" meaning that the mixture supplied by the computer will be
too:
a. Rich b. Lean
The following scan information is to be used to answer questions 56, 57, and 58:
IAC = 44
IAT = 27' C
MAF = 3 G/S
Timing = 10'
Codes = None
02 =.345 -.731
ECT = 1010 C
RPM = 657
TP = 0%
56. Technician A says the scan data is okay. Technician B says the throttle plate may require cleaning.
Which technician is correct?
a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B
57. Technician A says the TP sensor is misadjusted. Technician B says the 02S is degraded. Which
technician is correct?
a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B
58. Technician A says the thermostat may be defective. Technician B says the mass air flow sensor may
be defective. Which technician is correct?
a. Technician A only b. Technician B only c. Both Technicians A and B d. Neither Technician A nor B
59. HC:
a. Kills b. Smells c. Bums eyes d. Greenhouse gas
60. CO:
a. Kills b. Smells c. Bums eyes d. Greenhouse gas
61. NO,:
a. Kills b . Smells c . Bums eyes d. Greenhouse gas
62. C02:
a. Kills b. Smells c. Bums eyes d. Greenhouse gas
63. A technician is diagnosing an engine miss on a multi-port V-6. A ST-125 sparks on all cylinders. The
injector resistance on one bank reads 4.1 ohms and the other bank reads 2.9 ohms. The most likely cause
is:
a. A defective Quad driver in the PCM
b. One open injector
c. One shorted injector
d. One cracked spark plug
64. Two technicians are discussing excessive HC exhaust emissions. Technician A says that a stuck open
thermostat could be the cause. Technician B says that a lean misfire could be the cause. Which technician
is correct?
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
65. An engine running at 2000 RPM should have how much oil pressure?
a. 4 psi
b. 7 psi
C. 10 psi
d. 20 psi
66. Technician A says an engine with the following specifications is operating too rich. Technician B says
the engine is running too lean causing a lean misfire. Which technician is
correct? HC=287, C02=8.1, CO=2.6,02=0.1
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
67. Technician A says an engine with the following specifications is operating too rich. Technician B says
the engine is running too lean causing a lean misfire. Which technician is
correct? HC = 868, C02 = 7.8, CO = 0-01,02 = 8
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
68. Technician A says an engine with the following specifications is operating too rich. Technician B says
the engine is running too lean causing a lean misfire. Which technician is
correct? HC = 13, C02 = 16.3, CO = 0-0,02 = 0
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
69. Technician A says an engine with the following specifications is operating too rich. Technician B says
the engine is running too lean causing a lean misfire. Which technician is
correct? HC = 462, C02 = 15.4, CO = 0.3,02 = 5
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
70. A typical 02S sensor output can be measured for changing:
a. DC volts
b. AC volts
c. Ohms (resistance)
d. Frequency (Hertz)
71. The 02S is being measured on a fuel-injected V-6 engine. The reading is relatively steady ranging
from 0.388 to 0.460 volts. Adding propane increases the voltage to 0.687 volts and creating a vacuum
leak lowers the voltage to .312 volts. Technician A says the 02S may be defective. Technician B says this
is normal operation and that nothing is wrong. Which technician is correct?
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
72. An engine is operating with an 02S average reading of 0.312 volts. Technician A says the engine is
running rich. Technician B says the engine may have a vacuum leak. Which technician is correct?
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
73. The engine idle is rough and unstable. What is the most likely cause of this condition using the
following scan tool data?
SCAN TOOL DATA
Engine Coolant
Temperature Sensor (ECT)
212-F (I 00-C)
Actual Engine
Intake Air Temperature
Sensor (IAT)
86-F (30-C)
Desired Engine
760 RPM
Idle Air Control Valve
(IAQ
790 RPM
Evaporative Emission
Canister Solenoid (EVAP)
Manifold Absolute Pressure
Sensor (MAP)
2.0 V
Vehicle Speed Sensor
(VSS)
0 MPH
Torque Converter Clutch
Solenoid (TCQ
Off
Off
55 Counts
Malfunction Indicator
Lamp (MIL)
Off
I Measured Ignition Timing ('BTDC)
Diagnostic Trouble Codes
None
Base Timing: 12'
Open/Closed Loop
Closed
Actual Timing: 12'
a. Vacuum leak b. Dirty throttle plates C. Stuck open EGR valve d . Defective 02S
Throttle Position (TP) Sensor
0.45 V
Battery Voltage (13 f
14.7 V
EGR Valve Control Solenoid
(EGR)
0.0%
Heated Oxygen Sensor
(H02S)
401-930 mV
73. The engine idle is rough and unstable. What is the most likely cause of this condition using the
following scan tool data?
SCAN TOOL DATA
Intake Air Temperature
Manifold Absolute Pressure
Sensor (IAT)
Sensor (MAP)
Engine Coolant
Temperature Sensor (ECT)
Throttle Position (TP) Sensor
0.45 V
212-F (I 00-C)
Actual Engine
86-F (30-C)
Desired Engine
760 RPM
790 RPM
Idle Air Control Valve
2.0 V
Vehicle Speed Sensor
(VSS)
Battery Voltage (B+)
14.7 V
Evaporative Emission
Canister Solenoid (EVAP)
0 MPH
Torque Converter Clutch
Solenoid (TCQ
EGR Valve Control Solenoid
(EGR)
Off
Off
0.0%
Diagnostic Trouble Codes
Open/Closed Loop
Heated Oxygen Sensor
(H02S)
None
Closed
(IAQ
55 Counts
Malfunction Indicator
Lamp (MIL)
Off
Measured Ignition Timing ('BTDC)
a.
b.
c.
d.
Vacuum leak
Dirty throttle plates
Stuck open EGR valve
Defective 02S
401-930 mV
Base Timing: 12'
Actual Timing: 12'
74. The engine stalls occasionally. Technician A says the engine is operating too lean. Technician B
says that the throttle plates may be dirty restricting the amount of air into the engine at idle speed. Which
technician is correct?
SCAN TOOL DATA
Intake Air Temperature
Manifold Absolute Pressure
Sensor (IAT)
Sensor (MAP)
Engine Coolant
Temperature Sensor (ECT)
Throttle Position (TP) Sensor
0.45 V
212-F (I 00-C)
Actual Engine
86-F (30-C)
Desired Engine
760 RPM
790 RPM
Idle Air Control Valve
2.0 V
Vehicle Speed Sensor
(VSS)
Battery Voltage (B+)
14.7 V
Evaporative Emission
Canister Solenoid (EVAP)
0 MPH
Torque Converter Clutch
Solenoid (TCQ
EGR Valve Control Solenoid
(EGR)
Off
Off
0.0%
Diagnostic Trouble Codes
Open/Closed Loop
Heated Oxygen Sensor
(H02S)
None
Closed
(IAQ
55 Counts
Malfunction Indicator
Lamp (MIL)
Off
Measured Ignition Timing ('BTDC)
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
401-930 mV
Base Timing: 12'
Actual Timing: 12'
75. A vehicle surges and stumbles while accelerating and at cruise speed. The following 4-gas
infon-nation is available: HC = 335 PPM, CO = 0-01%, C02 = 8.2%, 02 = 6.1%. Technician A says that a
defective thermostat could be the cause. Technician B says that a coated (contaminated) 02S could be the
cause. Which technician is correct?
SCAN TOOL DATA
Intake Air Temperature
Manifold Absolute Pressure
Sensor (IAT)
Sensor (MAP)
Engine Coolant
Temperature Sensor (ECT)
Throttle Position (TP) Sensor
0.45 V
212-F (I 00-C)
Actual Engine
86-F (30-C)
Desired Engine
760 RPM
790 RPM
Idle Air Control Valve
2.0 V
Vehicle Speed Sensor
(VSS)
Battery Voltage (B+)
14.7 V
Evaporative Emission
Canister Solenoid (EVAP)
0 MPH
Torque Converter Clutch
Solenoid (TCQ
EGR Valve Control Solenoid
(EGR)
Off
Off
0.0%
Diagnostic Trouble Codes
Open/Closed Loop
Heated Oxygen Sensor
(H02S)
None
Closed
(IAQ
55 Counts
Malfunction Indicator
Lamp (MIL)
Off
Measured Ignition Timing ('BTDC)
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
401-930 mV
Base Timing: 12'
Actual Timing: 12'
76. A customer complains of poor fuel economy with the following specifications. Technician A says
that the then-nostat may be defective. Technician B says that the canister purge diaphragm may have a
leak. Which technician is correct?
SCAN TOOL DATA
Intake Air Temperature
Manifold Absolute Pressure
Sensor (IAT)
Sensor (MAP)
Engine Coolant
Temperature Sensor (ECT)
Throttle Position (TP) Sensor
0.45 V
212-F (I 00-C)
Actual Engine
86-F (30-C)
Desired Engine
760 RPM
790 RPM
Idle Air Control Valve
2.0 V
Vehicle Speed Sensor
(VSS)
Battery Voltage (B+)
14.7 V
Evaporative Emission
Canister Solenoid (EVAP)
0 MPH
Torque Converter Clutch
Solenoid (TCQ
EGR Valve Control Solenoid
(EGR)
Off
Off
0.0%
Diagnostic Trouble Codes
Open/Closed Loop
Heated Oxygen Sensor
(H02S)
None
Closed
(IAQ
55 Counts
Malfunction Indicator
Lamp (MIL)
Off
Measured Ignition Timing ('BTDC)
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
401-930 mV
Base Timing: 12'
Actual Timing: 12'
77. A customer complains of poor perfon-nance and lack of power with the following specifications.
Technician A says that a weak fuel pump could be the cause. Technician B says a clogged fuel filter could
be the cause. Which technician is correct?
SCAN TOOL DATA
Intake Air Temperature
Manifold Absolute Pressure
Sensor (IAT)
Sensor (MAP)
Engine Coolant
Temperature Sensor (ECT)
Throttle Position (TP) Sensor
0.45 V
212-F (I 00-C)
Actual Engine
86-F (30-C)
Desired Engine
760 RPM
790 RPM
Idle Air Control Valve
2.0 V
Vehicle Speed Sensor
(VSS)
Battery Voltage (B+)
14.7 V
Evaporative Emission
Canister Solenoid (EVAP)
0 MPH
Torque Converter Clutch
Solenoid (TCQ
EGR Valve Control Solenoid
(EGR)
Off
Off
0.0%
Diagnostic Trouble Codes
Open/Closed Loop
Heated Oxygen Sensor
(H02S)
None
Closed
(IAQ
55 Counts
Malfunction Indicator
Lamp (MIL)
Off
Measured Ignition Timing ('BTDC)
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
401-930 mV
Base Timing: 12'
Actual Timing: 12'
78. A customer's concern is poor fuel economy with the following specifications.
4-Gas Information:
HC = 386 PPM
CO ~ 3.86%
C02 = 7.76%
02 = 0%
Digital Meter Information:
02S = 500-1000 mV
Injector Pulse Width = 0.6 mS
SCAN TOOL DATA
Intake Air Temperature
Manifold Absolute Pressure
Sensor (IAT)
Sensor (MAP)
Engine Coolant
Temperature Sensor (ECT)
Throttle Position (TP) Sensor
0.45 V
212-F (I 00-C)
Actual Engine
86-F (30-C)
Desired Engine
760 RPM
790 RPM
Idle Air Control Valve
2.0 V
Vehicle Speed Sensor
(VSS)
Battery Voltage (B+)
14.7 V
Evaporative Emission
Canister Solenoid (EVAP)
0 MPH
Torque Converter Clutch
Solenoid (TCQ
EGR Valve Control Solenoid
(EGR)
Off
Off
0.0%
Diagnostic Trouble Codes
Open/Closed Loop
Heated Oxygen Sensor
(H02S)
None
Closed
(IAQ
55 Counts
Malfunction Indicator
Lamp (MIL)
Off
Measured Ignition Timing ('BTDC)
401-930 mV
Base Timing: 12'
Actual Timing: 12'
Technician A says the 02S may be defective. Technician B says the fuel pressure regulator could be
defective. Which technician is correct?
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
79. A customer's concern is poor fuel economy with a customized van with a V-8 and overdrive
automatic transmission with the following specifications:
4-Gas Information:
HC = 12 PPM
C02 = 17.2%
CO 0.1%
02 0-1%
SCAN TOOL DATA
Intake Air Temperature
Manifold Absolute Pressure
Sensor (IAT)
Sensor (MAP)
Engine Coolant
Temperature Sensor (ECT)
Throttle Position (TP) Sensor
0.45 V
212-F (I 00-C)
Actual Engine
86-F (30-C)
Desired Engine
760 RPM
790 RPM
Idle Air Control Valve
2.0 V
Vehicle Speed Sensor
(VSS)
Battery Voltage (B+)
14.7 V
Evaporative Emission
Canister Solenoid (EVAP)
0 MPH
Torque Converter Clutch
Solenoid (TCQ
EGR Valve Control Solenoid
(EGR)
Off
Off
0.0%
Diagnostic Trouble Codes
Open/Closed Loop
Heated Oxygen Sensor
(H02S)
None
Closed
(IAQ
55 Counts
Malfunction Indicator
Lamp (MIL)
Off
Measured Ignition Timing ('BTDC)
401-930 mV
Base Timing: 12'
Actual Timing: 12'
Technician A says that the thermostat may be defective. Technician B says that the engine is running too
rich. Which technician is correct?
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
80. Two technicians are discussing the cause of a random misfire DTC (P0300) with the specifications
below. Technician A says a defective or fouled spark plug could be the cause. Technician B says a
shorted ignition coil could be the case. Which technician is correct?
SCAN TOOL DATA
Intake Air Temperature
Manifold Absolute Pressure
Sensor (IAT)
Sensor (MAP)
Engine Coolant
Temperature Sensor (ECT)
Throttle Position (TP) Sensor
0.45 V
212-F (100-C)
Actual Engine
86-F (30-C)
Desired Engine
760 RPM
790 RPM
Idle Air Control Valve
2.0 V
Vehicle Speed Sensor
(VSS)
Battery Voltage (B+)
14.7 V
Evaporative Emission
Canister Solenoid (EVAP)
0 MPH
Torque Converter Clutch
Solenoid (TCQ
EGR Valve Control Solenoid
(EGR)
Off
Off
0.0%
Diagnostic Trouble Codes
Open/Closed Loop
Heated Oxygen Sensor
(H02S)
None
Closed
(IAQ
55 Counts
Malfunction Indicator
Lamp (MIL)
Off
Measured Ignition Timing ('BTDC)
a. Technician A only
b. Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
401-930 mV
Base Timing: 12'
Actual Timing: 12'