converter with the exception of the catalyst. See Fig. 5. The TWC
converter uses rhodium, with or without platinum, as its catalyst.
Rhodium helps reduce NOx emissions, as well as HC and CO.
Visually check for presence of catalytic converter(s). Also
check for presence of any required air supply system for the oxidizing
section of the converter. Check for external damage such as severe
dents, removed or damaged heat shields, etc. Check for pellets or
pieces of converter in the tailpipe.
Three-Way Catalyst + Oxidation Catalyst (TWC + OC)
This system contains a TWC converter and an OC converter in a
common housing, separated by a small air space. See Fig. 6. The 2
catalysts are referred to as catalyst beds. Exhaust gases pass through
the TWC first. The TWC bed performs the same function as it would as a
separate device, reducing all 3 emissions. As exhaust gases leave the
bed, they pass through the air space and into the second (OC)
converter catalyst bed.
Visually check for presence of catalytic converter(s). Check
for external damage such as severe dents, removed or damaged heat
shields, etc. Check for pellets or pieces of converter in the
tailpipe.
Fig. 6: Typical Three-Way + Oxidation Catalytic Converter
Courtesy of General Motors Corp.
FILL PIPE RESTRICTOR (FR)
A fuel tank fill pipe restrictor is used to prohibit the
introduction of leaded fuel into the fuel tank. Unleaded gasoline pump
dispensers have a smaller diameter nozzle to fit fuel tank of vehicle
requiring the use of unleaded fuel (vehicles equipped with catalytic
converter).
Visually inspect fill pipe restrictor(s) for tampering, i.e.,\
restrictor is oversize or the flapper is non-functional. If vehicle is
equipped with an auxiliary fuel tank, ensure auxiliary fuel tank is
also equipped with a fill pipe restrictor.
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
WIRING DIAGRAM COMPONENT LOCATIONS
When trying to locate a component in a wiring diagram and you
don't know the specific system where it is located, use this handy
component locator to find the system wiring diagram in which the
component is located. Then, go to that system and locate the component
within the wiring diagram.
For example, if you don't know the specific system in which
the ignition switch is located, look up ignition switch in the wiring
diagram component location tables and go to the appropriate wiring
diagram(s) which contain either full or partial views of the ignition
switch. The full view of the ignition switch is located in Power
Distribution.
The first listing for the component will be the full or most
complete view of the component. Additional listings will be partial
views of the component. Not all components are used on all models.
All components will have a partial view in Ground
Distribution and Power Distribution. Data Link Connectors show
connecting circuits between modules. Alternate names for components
may be listed in wiring diagram component locations tables.
WIRING DIAGRAM COMPONENT LOCATIONS TABLE
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Component Wiring Diagram
ABS Electronic Control Unit ....................... Anti-Lock Brakes
Data Link Connectors
ABS Hydraulic Unit ................................ Anti-Lock Brakes
Acceleration Sensor ............................... Anti-Lock Brakes
Accessory Delay Relay ................................ Power Windows
A/C Compressor Clutch Relay ..................... Engine Performance
A/C Sensor ...................................... Engine Performance
A/C Pressure Switch ............................. Engine Performance
Adaptive Lamp Control Module ....................... Exterior Lights
Air Bag(s) ................................ Air Bag Restraint System\
Air Bag Module ............................ Air Bag Restraint System
Air Bag Sensor(s) ......................... Air Bag Restraint System\
Air Injection Pump Relay ........................ Engine Performance
Air Temperature Sensor ............................ Overhead Console
Alternator (Generator) ..................... Generators & Regulators\
Anti-Theft Control Module ........................ Anti-Theft System
Starters
Autolamp Control Relay ........................... Headlight Systems
Daytime Running Lights
Automatic Shutdown (ASD) Relay .................. Engine Performance\
Generators & Regulators
Autostick Switch ................................ Engine Performance
Auxiliary Battery Relay .................... Generators & Regulators
Back-Up Lights ...................................... Back-Up Lights
Exterior Lights
Barometric (BARO) Pressure Sensor ............... Engine Performance\
Battery ......................................... Power Distribution
Battery Temperature Sensor ...................... Engine Performance
Body Control Module .......................... Body Control Computer
Anti-Theft System
Daytime Running Lights
Engine Performance
Headlight Systems
Warning Systems
Boost Control Solenoid .......................... Engine Performance
Boost Sensor .................................... Engine Performance
Brake Fluid Level Switch .................. Analog Instrument Panels
