Here are 12, not so secrets for service technicians that are new to vehicle emissions inspections and repairs.

According to the California Bureau of Automotive Repair, the top reasons that a vehicle fails the inspection are:

1) Incorrect Ignition Timing - It needs to be set at manufacturer's specifications.

2) Fuel Metering is Out of Specification - This includes carburetor-equipped vehicles and fule injected vehicles. This may also include a subset of computer and control components including injectors and oxygen sensors.

3) Faulty PCV system - Includes disconnected hoses. PCV valve - its flow is obstructed.

4) Faulty Gas Cap - The cap is leaking excessive Hydrocarbon vapors.

5) Inoperative Air Injection System, including air management valve and air injection pump.

6) Mis-routed vacuum lines.

7) Inperative thermostatic air cleaner.

8) Faulty Fuel Evaporative System - Evaporative Emissions Canister and hoses.

9) Faulty EGR System.

10) Vacuum Leaks - Includes vacuum lines, gasgets, hoses, etc.

11) Catalytic Converter - May be defective from overheating, being poisoned with lead, or plugged with carbon.

12) Oxides of Nitrogen Failures - Ignition timing, engine deposits, catalyst failure, EGR problems, coolant tempature.