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The Underhood Emission Label

The federal government requires vehicle manufactures to place this label in the vehicle's engine compartment. Normally it will be located on the bottom panel of the hood. It will look very similar to the one pictured below. This label will allow you to determine which emission components your vehicle is required to have.

The components will normally be listed in abbreviated form. Please use the abbreviations below and your vehicle's emissions label to learn about your car's required smog components.

Missing Label: Your vehicle will NOT fail the smog inspection if the Emissions Label is missing. A vehicle may have had its hood replaced and as a result may have lost its original emissions label.

Emission Label Abbreviations

AIR - Air Injection System
AIS - Air Injection System
TAC - Thermostatic Air Cleaner/Pre-heat Tube
EGR - Exhaust Recirculation Valve
O2 - Oxygen Sensor
H02 - Heated Oxygen Sensor
PCV - Positive Crankcase Ventilation
CAT - Catalytic Converter
TWC - Three Way Catalytic Converter
OC - Oxidation Catalyst (2-Way CAT)
EVAP - Fuel Evaporative System (Charcoal Canister)
MIL - Malfunction Indicator/Check Engine Lamp
SFI - Fuel Injection
OBDII - On-Board Diagnostics System II

Allow your engine to sufficiently cool down before you begin the inspection of any of these emissions components.

To help with your inspection at home select a component link from the top right side of this page to see it's image and description.

Required: All vehicles are required to have the PCV and EVAP systems installed and operational, regardless of whether these components are listed on the emission label or not.

Which Type Should I Choose?


These two emission systems are federal requirements and all vehicle manufactures must incorporate them into their vehicle's engine designs.

Note that these images may not pertain to your particular vehicle. They should however give you a rough idea of what the component/s in question should look similar to and where to find them.