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
The Underhood Emission
Recirculation Valve (EGR)
Crankcase Ventilation (PCV)
Canister (EVAP System)
Sensor (O2 Sensor)
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.