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Part 2. The Visual Inspection

During the visual portion of the smog inspection, the smog technician or mechanic will be looking for the presence and proper connection of several State of California required, emissions components. The visual portion of the smog test will include a Visible Smoke Test as well.

The smog technician must locate and verify that all emissions components are present and properly connected. Along with emissions components, the smog technician will also be looking for any defective or disconnected electrical connections, vacuum hoses and/or any pipe or plumbing which would effect engine performance and ultimately increase harmful smog emissions.

Note: During this part of the smog inspection process, the technician's inspection is only visual, and does not include testing emissions component for proper operation. The technician is required to simply locate the components visually, and ensure they are properly connected. If a vehicle fails the smog inspection, it is up to the vehicle's owner to have individual emissions components inspected for damage or defects.

A. Emissions Components

During your personal inspection at home, ensure all hoses and wires are in place and properly connected. The following is a list of emission components that will be inspected by the smog technician:

  • The Underhood Emission Label
  • Exhaust Gas Recirculation Valve (EGR)
  • Positive Crankcase Ventilation (PCV)
  • Charcoal Canister (EVAP System)
  • Catalytic Converter (CAT)
  • Oxygen Sensor (O2 Sensor)
  • Air Injection System (AIR)
  • Carburetor Pre-Heat Tube
  • Additional Emissions Components

    The following emissions components are also part of the visual portion of the smog inspection. The smog technician will need to see that they are present and properly connected. Most modern vehicles are equipped with most of these components.

    - Air Filter & Housing
    - Throttle Position Sensor (TPS)
    - Engine Coolant Temp Sensor (ECT)
    - Manifold Absolute Pressure (MAP)
    - Crankshaft Position Sensor (CKP)
    - Camshaft Position Sensor (CPS)
    - Intake Air Temperature Sensor (IAT)

    B. Visible Smoke Test

    Vehicles subject to a smog check require a visual inspection for excessive black or white smoke being emitted from the exhaust/tailpipe, as well as engine compartment.

    This test is in addition to the tailpipe emissions test. The smog technician will be required to enter his/her observation into the smog machine after the emissions test portion of the smog check.

    Excessive smoke, either black or white will cause a smog check failure. If your vehicle is emitting visible smoke, you will need to have the fault diagnosed and repaired before it can pass the smog check. Vehicles with severe engine damage may be emitting smoke from the engine compartment. This too will cause a visible smoke test failure.

    Which Type Should I Choose?



    What causes excessive black smoke? Visible black smoke may indicate one of two things.

    1. The engine is not burning fuel properly, leaving behind high amounts of Carbon Monoxide (CO), resulting in excessive black smoke being emitted from the tailpipe. These vehicles will experience increased fuel consumption as well.

    2. Engine oil is seeping into the combustion chambers. Oil is mixing with the fuel & air mixture, leaving behind high amounts of carbon, seen as excessive black smoke being emitted from the tailpipe. Oil seepage may occur due to defective piston rings, valve seals, or Positive Crank Ventilation (PCV) System.

    What causes excessive white smoke: Visible white smoke may indicate a burned or blown head gasket. Excessive white smoke (steam) is caused by water seepage into the combustion chambers, which on a running engine, operate around 2500f. Water has an opportunity to enter the combustion chambers through the head gasket, at the junction of an engine's valve head and block. This will typically cause overheating and white smoke in the exhaust coming out of your car's tailpipe.

    Note: Excessive white smoke should not be mistaken with normally emitted white smoke typically seen during cold days, and until an engine is properly warmed up. The smog check program is aware that vehicles may emit white smoke when cold, and ensures a vehicle is properly warmed up prior to administering the smog test.

    White smoke during startup or in cold weather is simply steam, and will not cause a smog check failure.