
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.