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Top Reasons for Emissions Test Failure

• Fuel Metering out of Specification (faulty computerized engine control, fuel injectors, carburetor.)
• Faulty Oxygen Sensor
• Ignition System Faults (spark plugs, wires, timing, distributor cap, etc.)
• Vacuum Leaks (vacuum lines, gaskets, etc.)
• Catalytic Converter Malfunction Engine Mechanical Problems (low compression, excessive blow-by, burned valves, etc.)
• Faulty EGR System
• Evaporative Emission Control System Faults (gas cap, evaporative emissions canister and controls.)
• Air Injection System Malfunction
• Faulty PCV System
• Faulty Thermostatic Air Cleaner

This illustration represents the most common emission control components in automobiles. As each automobile make varies in design, so will its engine and emission components. This poster is not designed to act as a sales tool for any of the parts illustrated and should not be used as such.

This illustration is being reprinted with the kind permission of the California Department of Consumer Affairs / Bureau of Automotive Repair and its Smog Check program.