Outside Air Temperature Sensor Below left headlamp.
Park/Neutral Position Sensor On left side of transmission.
Throttle Position Sensor On throttle body.
Vehicle Speed Sensor (VSS) On transmission tailshaft.
Volume Airflow Sensor In air cleaner duct (includes
intake air temperature sensor
& barometric pressure sensor).
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SOLENOIDS & SOLENOID VALVES
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Component Component Location \
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ABS Hydraulic Unit (w/Built-In
Solenoid Valve) In right rear corner of engine
compartment.
Cruise Control Actuator (w/Built-In
Control Valve & Release Valve)
(Calif.) In right rear of engine
compartment.
Cruise Control Actuator (w/Built-In
Control Valve & Release Valve)
(Federal) In left rear of engine
compartment.
EGR Solenoid In right rear of engine
compartment.
ELC 4-Speed Automatic Transmission
Control Solenoid Inside transmission.
Evaporative Emission Purge Solenoid On front of engine.
Evaporative Emission Ventilation
Solenoid In left rear of engine
compartment.
Solenoid Valves "A" & "B" In right side of engine
compartment.
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SWITCHES
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Component Component Location \
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A/T Fluid Temperature Switch On left side of transmission.
Brake Fluid Level Switch In brake master cylinder
reservoir.
Center Differential Lock Detection
Switch On transfer case.
Fig. 3: Typical Thermostatic Air Cleaner System
FUEL EVAPORATIVE SYSTEM (EVAP)
The EVAP system allows for proper fuel system ventilation
while preventing fuel vapors from reaching the atmosphere. This means
that vapors must be caught and stored while the engine is off, which
is when most fuel evaporation occurs. When the engine is started,
these fuel vapors can be removed from storage and burned. In most
systems, storage is provided by an activated charcoal (or carbon)
canister. See Fig. 4. On a few early systems, charcoal canisters are
not used. Instead, fuel vapors are vented into the PCV system and
stored inside the crankcase.
The main components of a fuel evaporation system are a sealed
fuel tank, a liquid-vapor separator and vent lines to a vapor-storing
canister filled with activated charcoal. The filler cap is normally
not vented to the atmosphere, but is fitted with a valve to allow both
pressure and vacuum relief.
Although a few variations do exist between manufacturers,
basic operation is the same for all systems. Check for presence of
vapor storage canister or crankcase storage connections when required.
Ensure required hoses, solenoids, etc., are present and connected
properly. Check for proper type fuel tank cap. Check for any non-OEM
or auxiliary fuel tanks for compliance and the required number of
evaporation canisters.
Fig. 4: Typical Fuel Evaporative System
CATALYTIC CONVERTERS
Oxidation Catalyst (OC)
This type of converter is the most common. It may use pellets
or monolith medium, depending upon application. See Fig. 5. Platinum
and palladium (or platinum alone) are used as catalyst in this type of\
converter.
Visually check for presence of catalytic converter(s). Check
for external damage such as severe dents, removed or damaged heat
shields, etc. Also check for pellets or pieces of converter in the
tailpipe.
Fig. 5: Typical Oxidation Catalytic Converter (Pellet Type) Shown;
Typical Three-Way Catalytic Converter Is Similar
Courtesy of General Motors Corp.
Three-Way Catalyst (TWC)
This type of converter is nearly identical to a conventional
EARLY FUEL EVAPORATION (EFE)
The EFE valve is actuated by either a vacuum actuator or a
bimetal spring (heat-riser type). The EFE valve is closed when engine
is cold. The closed valve restricts exhaust gas flow from the exhaust
manifold. This forces part of the exhaust gas to flow up through a
passage below the carburetor. As the exhaust gas quickly warms the
intake mixture, distribution is improved. This results in better cold
engine driveability, shorter choke periods and lower emissions.
Ensure EFE valve in exhaust manifold is not frozen or rusted
in a fixed position. On vacuum-actuated EFE system, check EFE thermal
vacuum valve and check valve(s). Also check for proper vacuum hose
routing. See Fig. 15.
Fig. 15: Typical Vacuum-Actuated EFE System
Courtesy of General Motors Corp.
EMISSION MAINTENANCE REMINDER LIGHT (EMR) (IF EQUIPPED)
CLUTCH PEDAL POSITION SWITCHES
COLD START INJECTORS
CONNECTORS
COOLANT
COOLANT RECOVERY TANKS
COOLING FAN MOTOR MODULES
COOLING FAN MOTOR RELAYS AND MODULES
COOLING FAN MOTOR RESISTORS
COOLING FAN MOTOR SENSORS AND SWITCHES
COOLING FAN MOTOR SWITCHES
COOLING FAN MOTORS
CRANKSHAFT POSITION SENSORS
DECEL VALVES
DEFLECTORS
DIP STICKS AND TUBES
DIP STICK TUBES
DISTRIBUTOR ADVANCES AND RETARDERS (MECHANICAL AND VACUUM)
DISTRIBUTOR BOOTS AND SHIELDS
DISTRIBUTOR CAPS
DISTRIBUTOR RETARDERS (MECHANICAL AND VACUUM)
DISTRIBUTOR ROTORS
DISTRIBUTOR SHIELDS
DISTRIBUTORS
EARLY FUEL EVAPORATION VALVES (HEAT RISER ASSEMBLIES)
EGR COOLERS
EGR EXHAUST MANIFOLD PASSAGES
EGR INTAKE AND EXHAUST MANIFOLD PASSAGES
EGR PLATES AND COOLERS
ELECTRONIC SPARK CONTROL MODULES
ELECTRONIC TRANSMISSION CONTROL DEVICES
ELECTRONIC TRANSMISSION FEEDBACK DEVICES
ENGINE COOLANT TEMPERATURE SENSORS
ENGINE COOLING SYSTEMS
ENGINE COVERS (OIL PAN, VALVE COVER, TIMING COVER)
ENGINE OIL
ENGINE OIL CANISTERS
ENGINE OIL COOLERS (EXTERNAL)
ENGINE OIL DRAIN PLUGS AND GASKETS
ENGINE OIL FILTERS AND CANISTERS
ENGINE OIL GASKETS
ENGINE OIL PRESSURE GAUGES (MECHANICAL)
EVAPORATIVE EMISSION (EVAP) CANISTER FILTERS
EVAPORATIVE EMISSION (EVAP) CANISTER PURGE DEVICES
EVAPORATIVE EMISSION (EVAP) CANISTERS
EVAPORATIVE EMISSION (EVAP) FEEDBACK DEVICES
EXHAUST GAS RECIRCULATION DEVICES
EXHAUST GAS RECIRCULATION FEEDBACK DEVICES
EXPANSION PLUGS
FAN CONTROL SENSORS
FUEL
FUEL ACCUMULATORS AND DAMPERS
FUEL AND COLD START INJECTORS
FUEL DAMPERS
FUEL DELIVERY CHECK VALVES
FUEL DISTRIBUTORS (BOSCH CIS)
FUEL FILLER NECKS AND RESTRICTORS
FUEL FILTERS
FUEL INJECTORS
FUEL LEVEL SENDERS7
FUEL PRESSURE REGULATORS
FUEL PUMPS (IN-TANK AND EXTERNAL, ELECTRICAL OR MECHANICAL)
FUEL RAILS
FUEL RESTRICTORS
Thrust washer missing ... C .. Require repair or replacement.
Thrust washer worn,
affecting performance .. A .. Require repair or replacement.
Thrust washer worn, not
affecting performance .. 1 .. Suggest repair or replacement.
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EARLY FUEL EVAPORATION VALVES (HEAT RISER ASSEMBLIES)
EARLY FUEL EVAPORATION VALVE (HEAT RISER ASSEMBLY) INSPECTION \
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Condition Code Procedure
Broken .................. A . Require replacement of affected
parts.
Diaphragm inoperative ... A .......... ( 1) Further inspection
required.
Leaking ................. A .. Require repair or replacement.
Noisy ................... 2 .. Suggest repair or replacement.
Seized .................. A . Require replacement of affected
parts.
Spring broken ........... B .......... Require replacement of
spring(s).
Spring inoperative ...... A ...... ( 2) Require replacement of
spring(s).
( 1) - Inoperative includes intermittent operation or out of
OEM specification. If the inoperative diaphragm is
separate from the heat riser, then require replacement
of the inoperative diaphragm. If the inoperative
diaphragm is part of the heat riser, then replace the
heat riser.
( 2) - Inoperative includes intermittent operation or out of OEM
specification.
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EGR COOLERS
See EGR PLATES AND COOLERS .
EGR EXHAUST MANIFOLD PASSAGES
See EGR INTAKE AND EXHAUST MANIFOLD PASSAGES .
EGR INTAKE AND EXHAUST MANIFOLD PASSAGES
EGR INTAKE AND EXHAUST MANIFOLD PASSAGE INSPECTION \
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Condition Code Procedure
Leaking ................. A .. Require repair or replacement.
Restricted, affecting
performance ............ A .. Require repair or replacement.
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EGR PLATES AND COOLERS
EGR PLATE AND COOLER INSPECTION \
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Condition Code Procedure
Leaking ................. A .. Require repair or replacement.
Further inspection required.
Canister attaching
hardware broken ........ A ... Require repair or replacement
of hardware.
Canister attaching
hardware loose ......... A ................. Require repair.
Canister attaching
hardware missing ....... C ............ Require replacement.
Canister attaching
hardware not
functioning ............ A ... Require repair or replacement
of hardware.
Center tube collapsed ... A ........ (2) Require replacement.
Further inspection required.
Contaminated ............ A ...... ( 3) Require replacement of
oil and filter.
Dented .................. 2 ........ ( 4) Suggest replacement.
Further inspection required.
Leaking ................. A .. Require repair or replacement.
Maintenance intervals ... 3 ... Suggest replacement to comply
with vehicle's OEM recommended
service intervals.
( 1) - Inspect pressure relief valve.
( 2) - Inspect bypass.
( 3) - Determine cause of contamination, such as engine coolant,
fuel, metal particles, or water when changing oil. Require
repair or replacement.
( 4) - Determine cause, such as broken motor mount.
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ENGINE OIL GASKETS
See ENGINE OIL DRAIN PLUGS AND GASKETS .
ENGINE OIL PRESSURE GAUGES (MECHANICAL)
ENGINE OIL PRESSURE GAUGE (MECHANICAL) INSPECTION \
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Condition Code Procedure
Indicates out of range .. B .......... ( 1) Further inspection
required.
Inoperative ............. A .......... ( 2) Further inspection
required.
Leaking ................. A .. Require repair or replacement.
Reads inaccurately ...... 2 .. Suggest repair or replacement.
( 1) - Gauge may indicate problem with contaminated oil, level,
pressure, or temperature, or problem with gauge.
( 2) - Gauge may indicate problem with contaminated oil, level,
pressure, or temperature, or problem with gauge.
Inoperative includes intermittent operation, out of OEM
specification, or out of range. Further inspection
required to determine cause.
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EVAPORATIVE EMISSION (EVAP) CANISTER FILTERS
EVAPORATIVE EMISSION (EVAP) CANISTER FILTER INSPECTION \
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Condition Code Procedure
Attaching hardware
broken ................. A ... Require repair or replacement
of hardware.
Attaching hardware
missing ................ C .......... Require replacement of
hardware.
Attaching hardware not
functioning ............ A ... Require repair or replacement
of hardware.
Maintenance interval .... 3 ... Suggest replacement to comply
with OEM recommended service
interval.
Missing ................. C ............ Require replacement.
Restricted, affecting
performance ............ A ............ Require replacement.
Restricted, not affecting
performance ............ 1 ............ Suggest replacement.
Water-contaminated ...... A ............ Require replacement.
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EVAPORATIVE EMISSION (EVAP) CANISTER PURGE DEVICES
EVAPORATIVE EMISSION (EVAP) CANISTER PURGE DEVICE INSPECTION \
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Condition Code Procedure
Attaching hardware
missing ................ C .......... Require replacement of
hardware.
Attaching hardware
threads damaged ........ A ... Require repair or replacement
of hardware.
Attaching hardware
threads stripped
(threads missing) ...... A ... Require repair or replacement
of hardware.
Connector broken ........ A .. Require repair or replacement.
Connector (Weatherpack
type) leaking .......... A .. Require repair or replacement.
Connector melted ........ A ........... ( 1) Require repair or
replacement.
Connector missing ....... C ............ Require replacement.
Contaminated ............ A ........... ( 2) Require repair or
replacement.
Inoperative ............. B ........... ( 3) Require repair or
replacement. Further
inspection required.
Leaking ................. A .. Require repair or replacement.
Missing ................. C ............ Require replacement.
Resistance out of
specification .......... B .. Require repair or replacement.
Restricted, affecting
performance ............ A .. Require repair or replacement.
Terminal broken ......... A .. Require repair or replacement.
Terminal burned, affecting
performance ............ A ........... ( 1) Require repair or
replacement.
Terminal burned, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal corroded,
affecting performance .. A .. Require repair or replacement.
Terminal corroded, not
affecting performance .. 2 .. Suggest repair or replacement.