Halderman J.D., Linder J. Automotive Fuel and Emissions Control Systems
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FUEL-INJECTION SYSTEM DIAGNOSIS AND SERVICE 301
STEP BY STEP
To help make good electrical contact with the terminals
without doing any harm, select the proper-size terminal
from the terminal assortment.
7
Insert the terminals into the relay socket in 30 and 87.
8
To check for voltage at terminal 30, use a test light or
a voltmeter. Start by connecting the alligator clip of the
test light to the positive (⫹) terminal of the battery.
9
Touch the test light to the negative (⫺) terminal of
the battery or a good engine ground to check the
test light.
10
Use the test light to check for voltage at terminal
30 of the relay. The ignition may have to be in the
on (run) position.
11
To check to see if the electric fuel pump can be op-
erated from the relay contacts, use a fused jumper
wire and touch the relay contacts that correspond
to terminals 30 and 87 of the relay.
12
CONTINUED
302 CHAPTER 23
FUEL-PUMP RELAY CIRCUIT DIAGNOSIS (CONTINUED)
Connect the leads of the meter to contacts 30
and 87 of the relay socket. The reading of
4.7 amperes is okay because the specification
is 4 to 8 amperes.
13
Set the meter to read ohms (Ω) and measure the
resistance of the relay coil. The usual reading for
most relays is between 60 and 100 ohms.
14
Measure between terminal 30 and 87a. Terminal
87a is the normally closed contact, and there
should be little, if any, resistance between these
two terminals, as shown.
15
To test the normally open contacts, connect one
meter lead to terminal 30 and the other lead to
terminal 87. The ohmmeter should show an open
circuit by displaying OL.
16
Connect a fused jumper wire to supply 12 volts to
terminal 86 and a ground to terminal 85 of the re-
lay. If the relay clicks, then the relay coil is able to
move the armature (movable arm) of the relay.
17
After testing, be sure to reinstall the relay and the
relay cover.
18
FUEL-INJECTION SYSTEM DIAGNOSIS AND SERVICE 303
FUEL-INJECTOR CLEANING
Start the fuel-injector cleaning process by bringing the
vehicle’s engine up to operating temperature. Shut off
the engine, remove the cap from the fuel rail test port,
and install the appropriate adapter.
1
The vehicle’s fuel pump is disabled by removing its
relay or fuse. In some cases, it may be necessary to
disconnect the fuel pump at the tank if the relay or fuse
powers more than just the pump.
2
Turn the outlet valve of the canister to the OFF or
CLOSED position.
3
Remove the fuel-injector cleaning canister’s top and
regulator assembly. Note that there is an O-ring seal
located here that must be in place for the canister’s top
to seal properly.
4
Pour the injection system cleaning fluid into the open
canister. Rubber gloves are highly recommended for
this step as the fluid is toxic.
5
Replace the canister’s top (making sure it is tight) and
connect its hose to the fuel rail adapter. Be sure that the
hose is routed away from exhaust manifolds and other
hazards.
6
CONTINUED
304 CHAPTER 23
FUEL-INJECTOR CLEANING (CONTINUED)
Hang the canister from the vehicle’s hood and adjust
the air pressure regulator to full OPEN position (CCW).
7
Canister pressure should be adjusted to 5 PSI below
system fuel pressure. An alternative for return-type
systems is to block the fuel return line to the tank.
9
Connect shop air to the canister and adjust the air pres-
sure regulator to the desired setting. Canister pressure
can be read directly from the gauge.
8
Start the vehicle’s engine and let run at
1,000 to 1,500 RPM. The engine is now running on
fuel-injector cleaning fluid provided by the canister.
11
Continue the process until the canister is empty
and the engine stalls. Remove the cleaning equip-
ment, enable the vehicle’s fuel pump, and run the
engine to check for leaks.
12
Open the outlet valve on the canister.
10
FUEL-INJECTION SYSTEM DIAGNOSIS AND SERVICE 305
4. A noid light can be used to check for the presence of an
injector pulse.
5. Injectors can be tested for resistance and should be within
0.3 to 0.4 ohm of each other.
6. Different designs of injectors have a different scope wave-
form depending on how the computer pulses the injector
on and off.
7. An idle air control unit controls idle speed and can be
tested for proper operation using a scan tool or scope.
1. A typical throttle-body fuel injector uses a computer-
controlled injector solenoid to spray fuel into the throttle-
body unit above the throttle plates.
2. A typical port fuel-injection system uses an individual fuel
injector for each cylinder and squirts fuel directly into
the intake manifold about 3 inches (80 mm) from the
intake valve.
3. A typical fuel-injection system fuel pressure should not
drop more than 20 PSI in 20 minutes.
SUMMARY
3. Describe why it may be necessary to clean the throttle
plate of a port fuel-injected engine.
1. List the ways fuel injectors can be tested.
2. List the steps necessary to test a fuel-pressure regulator.
REVIEW QUESTIONS
6. The fuel pressure drops rapidly when the engine is turned
off. Technician A says that one or more injectors could be
leaking. Technician B says that a defective check valve
in the fuel pump could be the cause. Which technician is
correct?
a. Technician A only c. Both Technicians A and B
b. Technician B only d. Neither Technician A nor B
7. In a typical port fuel-injection system, which injectors are
most subject to becoming restricted?
a. Any of them equally
b. The injectors at the end of the rail on a returnless system
c. The injectors at the bends in the rail
d. Either b or c
8. What component pulses the fuel injector on most vehicles?
a. Electronic control unit (computer)
b. Ignition module
c. Crankshaft sensor
d. Both b and c
9. Fuel-injection service is being discussed. Technician A
says that the throttle plate(s) should be cleaned. Techni-
cian B says that the fuel rail should be cleaned. Which
technician is correct?
a. Technician A only c. Both Technicians A and B
b. Technician B only d. Neither Technician A nor B
10. If the throttle plate needs to be cleaned, what symptoms
will be present regarding the operation of the engine?
a. Stalls c. Hesitation on acceleration
b. Rough idle d. All of the above
1.
Most port fuel-injected engines operate on how much fuel
pressure?
a. 3 to 5 PSI (21 to 35 kPa)
b. 9 to 13 PSI (62 to 90 kPa)
c. 35 to 45 PSI (240 to 310 kPa)
d. 55 to 65 PSI (380 to 450 kPa)
2. Fuel injectors can be tested using ______________ .
a. An ohmmeter c. A scope
b. A stethoscope d. All of the above
3. Throttle-body fuel-injection systems use what type of
injector driver?
a. Peak and hold
b. Saturated switch
c. Pulse-width modulated
d. Pulsed
4. Port fuel-injection systems generally use what type of in-
jector driver?
a. Peak and hold
b. Saturated switch
c. Pulse-width modulated
d. Pulsed
5. The vacuum hose from the fuel-pressure regulator was re-
moved from the regulator and gasoline dripped out of the
hose. Technician A says that is normal and that everything
is okay. Technician B says that one or more of the injectors
may be defective, causing the fuel to get into the hose.
Which technician is correct?
a. Technician A only
b.
Technician B only
c. Both Technicians A and B
d. Neither Technician A nor B
CHAPTER QUIZ
306 CHAPTER 24
chapter
VEHICLE EMISSION
STANDARDS
AND TESTING
24
OBJECTIVES: After studying Chapter 24 , the reader should be able to: • Prepare for ASE Engine Performance (A8)
certification test content area “D” (Emissions Control Systems Diagnosis and Repair) and ASE L1 certification test content area
“F” (I/M Failure Diagnosis). • Discuss emission standards. • Identify the reasons why excessive amounts of HC, CO, and NO
X
exhaust emissions are created. • Describe how to baseline a vehicle after an exhaust emission failure. • List acceptable levels
of HC, CO, CO
2
, and O
2
with and without a catalytic converter. • List four possible causes for high readings for HC, CO, and NO
X
.
KEY TERMS: Acceleration simulation mode (ASM) 309 • ASM 25/25 test 309 • ASM 50/15 test 309 • Clean Air Act
Amendments (CAAA) 306 • Federal Test Procedure (FTP) 308 • I/M 240 test 310 • Lean indicator 313 • Non-methane
hydrocarbon (NMHC) 311 • Ozone 313 • Rich indicator 312 • Sealed Housing for Evaporative Determination (SHED) test 308
• Smog 313 • State Implementation Plan (SIP) 308
EMISSION STANDARDS
IN THE UNITED STATES
In the United States, emissions standards are managed by the
Environmental Protection Agency (EPA) as well as some U.S.
state governments. Some of the strictest standards in the world
are formulated in California by the California Air Resources
Board (CARB).
TIER 1 AND TIER 2 Federal emission standards are set
by the Clean Air Amendments (CAAA) of 1990 grouped by
tier. All vehicles sold in the United States must meet Tier 1
standards that went into effect in 1994 and are the least strin-
gent. Additional Tier 2 standards have been optional since
2001 and was fully phased in by 2009. The current Tier 1
standards are different between automobiles and light trucks
(SUVs, pickup trucks, and minivans), but Tier 2 standards will
be the same for both types of vehicles.
There are several ratings that can be given to vehicles, and
a certain percentage of a manufacturer’s vehicles must meet
different levels in order for the company to sell its products in
affected regions. Beyond Tier 1, and in order by stringency, are
the following levels:
TLEV Transitional Low-Emission Vehicle. More strin-
gent for HC than Tier 1.
LEV (also known as LEV I ): Low-Emission Vehicle, an
intermediate California standard about twice as stringent
as Tier 1 for HC and NO
X
.
FIGURE 24–1 The underhood decal showing that this Lexus
RX-330 meets both national (Tier 2; BIN 5) and California LEV-II
(ULEV) regulation standards.
ULEV (also known as ULEV I): Ultra-Low-Emission
Vehicle. A stronger California standard emphasizing
very low HC emissions.
ULEV II: Ultra-Low-Emission Vehicle. A cleaner-than-
average vehicle certified under the Phase II LEV standard.
Hydrocarbon and carbon monoxide emissions levels are
nearly 50% lower than those of a LEV II-certified vehicle.
SEE FIGURE 24–1.
SULEV: Super-Ultra-Low-Emission Vehicle. A Cali-
fornia standard even tighter than ULEV, including much
VEHICLE EMISSION STANDARDS AND TESTING 307
lower HC and NO
X
emissions; roughly equivalent to Tier 2
Bin 2 vehicles.
ZEV: Zero-Emission Vehicle. A California standard pro-
hibiting any tailpipe emissions. The ZEV category is largely
restricted to electric vehicles and hydrogen-fueled vehicles.
In these cases, any emissions that are created are produced
at another site, such as a power plant or hydrogen reform-
ing center, unless such sites run on renewable energy.
NOTE: A battery-powered electric vehicle charged
from the power grid will still be up to 10 times
cleaner than even the cleanest gasoline vehicles
over their respective lifetimes.
PZEV: Partial Zero-Emission Vehicle. Compliant with
the SULEV standard; additionally has near-zero evapora-
tive emissions and a 15 year/150,000 mile warranty on its
emission control equipment.
Tier 2 standards are even more stringent. Tier 2 variations
are appended with “II,” such as LEV II or SULEV II. Other cat-
egories have also been created:
ILEV: Inherently Low-Emission Vehicle- a vehicle certi-
fied to meet the transitional low-emission vehicle standards
established by the California Air Resources Board (CARB).
AT-PZEV: Advanced Technology Partial Zero-
Emission Vehicle. If a vehicle meets the PZEV standards
and is using high-technology features, such as an electric
motor or high-pressure gaseous fuel tanks for com-
pressed natural gas, it qualifies as an AT-PZEV. Hybrid
electric vehicles such as the Toyota Prius can qualify, as
can internal combustion engine vehicles that run on natu-
ral gas (CNG), such as the Honda Civic GX. These vehi-
cles are classified as “partial” ZEV because they receive
partial credit for the number of ZEV vehicles that auto-
makers would otherwise be required to sell in California.
NLEV: National Low-Emission Vehicle. All vehicles
nationwide must meet this standard, which started in 2001.
FEDERAL EPA BIN NUMBER The higher the tier number,
the newer the regulation; the lower the bin number, the cleaner the
vehicle. The Toyota Prius is a very clean Bin 3, while the Hummer
H2 is a dirty Bin 11.
SEE CHARTS 24–1 THROUGH 24–3.
SMOG EMISSION INFORMATION New vehicles are
equipped with a sticker that shows the relative level of smog-
causing emissions created by the vehicle compared to others on
the market. Smog-causing emissions include unburned hydro-
carbons (HC) and oxides of nitrogen (NO
X
). SEE FIGURE 24–2.
CALIFORNIA STANDARDS The pre-2004 California Air
Resources Board (CARB) standards as a whole were known
as LEV I. Within that, there were four possible ratings: Tier 1,
TLEV, LEV, and ULEV. The newest CARB rating system (since
January 1, 2004) is known as LEV II. Within that rating system
there are three primary ratings: LEV, ULEV, and SULEV. States
other than California are given the option to use the federal EPA
standards, or they can adopt California’s standards.
CHART 24–1
EPA Tier 2—120,000-Mile Tailpipe Emission Limits. After
January 2007, the highest allowable bin is 7. NMOG stands for
non-methane organic gases which is a measure of all gases
except those often created naturally by animals.
Source: Data compiled from the Environmental Protection
Agency (EPA).
NOTE: The bin number is determined by the type and weight of the
vehicle.
CERTIFICATION LEVEL NMOG (G/MI) CO (G/MI) NO
X
(G/MI)
Bin 1 0.0 0.0 0.0
Bin 2 0.010 2.1 0.02
Bin 3 0.055 2.1 0.03
Bin 4 0.070 2.1 0.04
Bin 5 0.090 4.2 0.07
Bin 6 0.090 4.2 0.10
Bin 7 0.090 4.2 0.15
Bin 8a 0.125 4.2 0.20
Bin 8b 0.156 4.2 0.20
Bin 9a 0.090 4.2 0.30
Bin 9b 0.130 4.2 0.30
Bin 9c 0.180 4.2 0.30
Bin 10a 0.156 4.2 0.60
Bin 10b 0.230 6.4 0.60
Bin 10c 0.230 6.4 0.60
Bin 11 0.230 7.3 0.90
CHART 24–2
Air Pollution Score
Source: Courtesy of the Environmental Protection Agency (EPA).
U.S. EPA VEHICLE INFORMATION PROGRAM
(THE HIGHER THE SCORE, THE LOWER THE EMISSIONS)
SELECTED EMISSIONS STANDARDS SCORE
Bin 1 and ZEV 10
PZEV 9.5
Bin 2 9
Bin 3 8
Bin 4 7
Bin 5 and LEV II cars 6
Bin 6 5
Bin 7 4
Bin 8 3
Bin 9a and LEV I cars 2
Bin 9b 2
Bin 10a 1
Bin 10b and Tier 1 cars 1
Bin 11 0
308 CHAPTER 24
FIGURE 24–2 This label on a Toyota Camry hybrid shows the
relative smog-producing emissions, but this does not include
carbon dioxide (CO
2
), which may increase global warming.
CHART 24–3
Greenhouse Gas Score
Source: Courtesy of the Environmental Protection Agency (EPA).
*CNG assumes a gallon equivalent of 121.5 cubic feet.
MINIMUM FUEL ECONOMY (MPG) COMBINED
CITY-HIGHWAY LABEL VALUE
SCORE GASOLINE DIESEL E-85 LPG CNG*
10 44 50 31 28 33
9 36 41 26 23 27
8 30 35 22 20 23
7 26 30 19 17 20
6 23 27 17 15 18
5 21 24 15 14 16
4 19 22 14 12 14
3 17 20 12 11 13
2 16 18 — — 12
1 15 17 11 10 11
0 14 16 10 9 10
EUROPEAN STANDARDS
Europe has its own set of standards that vehicles must meet,
which includes the following tiers:
Euro I (1992–1995)
Euro II (1995–1999)
Euro III (1999–2005)
Euro IV (2005–2008)
Euro V (2008)
Vehicle emission standards and technological advance-
ments have successfully reduced pollution from cars and trucks
by about 90% since the 1970s. Unfortunately, there currently
are more vehicles on the road, and they are being driven more
miles each year, partially offsetting the environmental benefits
of individual vehicle emissions reductions.
The Clean Air Act Amendments require enhanced Inspection and
Maintenance (I/M) programs in areas of the country that have
the worst air quality and the Northeast Ozone Transport region.
The states must submit to the EPA a State Implementation
Plan (SIP) for their programs. Each enhanced I/M program is
required to include as a minimum the following items:
Computerized emission analyzers
Visual inspection of emission control items
Minimum waiver limit (to be increased based on the infla-
tion index)
Remote on-road testing of one-half of 1% of the vehicle
population
Registration denial for vehicles not passing an I/M test
Denial of waiver for vehicles that are under warranty or
that have been tampered with
Annual inspections
OBD-II systems check for 1996 and newer vehicles
FEDERAL TEST PROCEDURE (FTP) The Federal Test
Procedure (FTP) is the test used to certify all new vehicles
before they can be sold. Once a vehicle meets these standards,
it is certified by the EPA for sale in the United States. The FTP
test procedure is a loaded-mode test lasting for a total duration
of 505 seconds and is designed to simulate an urban driving
trip. A cold start-up representing a morning start and a hot start
after a soak period is part of the test. In addition to this drive
cycle, a vehicle must undergo evaporative testing. Evaporative
emissions are determined using the Sealed Housing for
Evaporative Determination (SHED) test, which measures the
evaporative emissions from the vehicle after a heat-up period
representing a vehicle sitting in the sun. In addition, the vehicle
is driven and then tested during the hot soak period.
NOTE: A SHED is constructed entirely of stainless steel.
The walls, floors, and ceiling, plus the door, are all con-
structed of stainless steel because it does not absorb
hydrocarbons, which could offset test results.
The FTP is a much more stringent test of vehicle emis-
sions than is any test type that uses equipment that measures
percentages of exhaust gases. The federal emission standards
for each model year vehicle are the same for that model regard-
less of what size engine the vehicle is equipped with. This is
why larger V-8 engines often are equipped with more emission
control devices than smaller 4- and 6-cylinder engines.
EXHAUST ANALYSIS
TESTING
VEHICLE EMISSION STANDARDS AND TESTING 309
I/M TEST PROGRAMS There are a variety of I/M testing
programs that have been implemented by the various states.
These programs may be centralized testing programs or decen-
tralized testing programs. Each state is free to develop a testing
program suitable to their needs as long as they can demon-
strate to the EPA that their plan will achieve the attainment lev-
els set by the EPA. This approach has led to a variety of different
testing programs.
SEE FIGURE 24–3.
VISUAL TAMPERING CHECKS Visual tampering checks
may be part of an I/M testing program and usually include
checking for the following items:
Catalytic converter
Fuel tank inlet restrictor
Exhaust gas recirculation (EGR)
Evaporative emission system
Air-injection reaction system (AIR)
Positive crankcase ventilation (PCV)
If any of these systems are missing, not connected, or tam-
pered with, the vehicle will fail the emissions test and will have
to be repaired/replaced by the vehicle owner before the vehicle
can pass the emission test. Any cost associated with repairing
or replacing these components may not be used toward the
waiver amount required for the vehicle to receive a waiver.
ONE-SPEED AND TWO-SPEED IDLE TEST The one-
speed and two-speed idle test measures the exhaust emissions
from the tailpipe of the vehicle at idle and/or at 2,500 RPM.
This uses stand-alone exhaust gas sampling equipment that
measures the emissions in percentages. Each state chooses
the standards that the vehicle has to meet in order to pass
the test. The advantage to using this type of testing is that the
equipment is relatively cheap and allows states to have decen-
tralized testing programs because many facilities can afford the
necessary equipment required to perform this test.
LOADED-MODE TEST The loaded-mode test uses a
dynamometer that places a “single weight” load on the vehicle.
The load applied to the vehicle varies with the speed of the
vehicle. Typically, a 4-cylinder vehicle speed would be 24 mph,
a 6-cylinder vehicle speed would be 30 mph, and an 8-cylinder
vehicle speed would be 34 mph. Conventional stand-alone
sampling equipment is used to measure HC and CO emissions.
This type of test is classified as a Basic I/M test by the EPA.
SEE FIGURE 24–4.
ACCELERATION SIMULATION MODE (ASM) The
ASM-type of test uses a dynamometer that applies a heavy load
on the vehicle at a steady-state speed. The load applied to the
vehicle is based on the acceleration rate on the second simulated
hill of the FTP. This acceleration rate is 3.3 mph/sec/sec (read as
3.3 mph per second per second, which is the unit of acceleration).
There are different ASM tests used by different states.
The ASM 50/15 test places a load of 50% on the vehicle at
a steady 15 mph. This load represents 50% of the horsepower
required to simulate the FTP acceleration rate of 3.3 mph/sec.
This type of test produces relatively high levels of NO
X
emissions;
therefore, it is useful in detecting vehicles that are emitting exces-
sive NO
X
.
The ASM 25/25 test places a 25% load on the vehicle while
it is driven at a steady 25 mph. This represents 25% of the load
required to simulate the FTP acceleration rate of 3.3mph/sec.
Because this applies a smaller load on the vehicle at a higher
speed, it will produce a higher level of HC and CO emissions
than the ASM 50/15. NO
X
emissions will tend to be lower with
this type of test.
FIGURE 24–3 Photo of a sign taken at an emissions test
facility.
FIGURE 24–4 A vehicle being tested during an enhanced
emission test.
310 CHAPTER 24
5
0
40
30
20
10
0
0 50 100 150 200
TIME (SEC)
SPEED (MPH)
FIGURE 24–5 Trace showing the Inspection/Maintenance 240 test. The test duplicates an urban test loop around Los Angeles,
California. The first “hump” in the curve represents the vehicle being accelerated to about 20 mph, then driving up a small hill to
about 30 mph and coming to a stop at 94 seconds. Then, the vehicle accelerates while climbing a hill and speeding up to about
50 mph during this second phase of the test.
I/M 240 TEST The I/M 240 test is the EPA’s enhanced test.
It is actually a portion of the 505-second FTP test used by the
manufacturers to certify their new vehicles. The “240” stands for
240 seconds of drive time on a dynamometer. This is a loaded-
mode transient test that uses constant volume sampling equip-
ment to measure the exhaust emissions in mass just as is done
during the FTP. The I/M 240 test simulates the first two hills of the
FTP drive cycle.
FIGURE 24–5 shows the I/M 240 drive trace.
OBD-II TESTING In 1999, the EPA requested that states
adopt OBD-II systems testing for 1996 and newer vehicles.
The OBD-II system is designed to illuminate the MIL and store
trouble codes any time a malfunction exists that would cause
the vehicle emissions to exceed 1 1/2 times the FTP limits. If
the OBD-II system is working correctly, the system should be
able to detect a vehicle failure that would cause emissions to
increase to an unacceptable level. The EPA has determined that
the OBD-II system should detect emission failures of a vehicle
even before that vehicle would fail an emissions test of the
type that most states are employing. Furthermore, the EPA has
determined that, as the population of OBD-II-equipped vehicles
increases and the population of older non-OBD-II-equipped
vehicles decreases, tailpipe testing will no longer be necessary.
The OBD-II testing program consists of a computer that
can scan the vehicle OBD-II system using the DLC connector.
The technician first performs a visual check of the vehicle MIL
light to determine if it is working correctly. Next, the computer
is connected to the vehicle’s DLC connector. The computer will
scan the vehicle OBD-II system and determine if there are any
codes stored that are commanding the MIL light on. In addition,
it will scan the status of the readiness monitors and determine if
they have all run and passed. If the readiness monitors have all
run and passed, it indicates that the OBD-II system has tested
all the components of the emission control system. An OBD-II
vehicle would fail this OBD-II test if the following occur:
The MIL light does not come on with the key on, engine off.
The MIL is commanded on.
A number (varies by state) of the readiness monitors have
not been run.
If none of these conditions are present, the vehicle will
pass the emissions test.
REMOTE SENSING The EPA requires that, in high-
enhanced areas, states perform on-the-road testing of vehicle
emissions. The state must sample 0.5% of the vehicle popula-
tion base in high-enhanced areas. This may be accomplished
by using a remote sensing device. This type of sensing may be
done through equipment that projects an infrared light through
the exhaust stream of a passing vehicle. The reflected beam
can then be analyzed to determine the pollutant levels coming
from the vehicle. If a vehicle fails this type of test, the vehicle
owner will receive notification in the mail that he or she must
take the vehicle to a test facility to have the emissions tested.
RANDOM ROADSIDE TESTING Some states may imple-
ment random roadside testing that would usually involve visual
checks of the emission control devices to detect tampering.
Obviously, this method is not very popular, as it can lead to
traffic tie-ups and delays on the part of commuters.
Exhaust analysis is an excellent tool to use for the diagno-
sis of engine performance concerns. In areas of the country that
require exhaust testing to be able to get license plates, exhaust
analysis must be able to do the following:
Establish a baseline for failure diagnosis and service
Identify areas of engine performance that are and are not
functioning correctly
Determine that the service and repair of the vehicle have
been accomplished and are complete