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What if Your Vehicle Fails?


Diagnosing a vehicle for emission inspection failure can be complicated. As an Idaho motorist, you are free to select a qualified repair technician or repair the vehicle yourself. However, due to the complexity of today's vehicles, you should strongly consider having your vehicle repairs performed by a qualified technician who is experienced in diagnosing and repairing vehicle emission systems.

Vehicles not passing the inspection will receive a vehicle inspection report with the reason(s) the vehicle has failed. After appropriate repairs are made to the vehicle, you are entitled to one free retest within thirty (30) days of the initial inspection at any of the vehicle inspection station within Canyon County or Kuna.

When returning for a retest, 1981 - 1995 gasoline vehicles and all diesel vehicles will be subject to the entire anti-tampering and appropriate emissions test. 1996 and newer gasoline and 1998 and newer diesel vehicles will only be subject to the portion of the inspection for which the vehicle originally failed.

If the vehicle fails the retest, a vehicle inspection report will be provided indicating the reason(s) for failure. The vehicle must have the necessary repairs made in order to pass the vehicle inspection.

The next retest will cost $10.00 with the following retest (if needed) free. All subsequant retests are paid until the vehicle passes.


Exhaust Gas Recirculation (EGR) - recirculates exhaust gases into intake manifold and is controlled by vacuum pressure.

Spark Controls (SPK) - ensure that air/fuel mixture is ignited at the best possible moment to provide optimum efficiency, power, and cleaner emissions.

Positive Crankcase Ventilation (PCV) - controls the flow of crankcase fumes into the intake manifold while preventing gases and flames from traveling in the opposite direction.

Thermostatic Air Cleaner (ACL) - supplies warm air to air intake during cold engine operation. This system is only active during cold engine warm-up.

Fuel Evaporative System (EVAP) - allows for proper fuel system ventilation while preventing fuel vapors from reaching the atmosphere. Catches and store vapors until engine is restarted. Vapors are then removed from storage and burned.

Catalytic Converters (OC)(TWC) - remove/reduce NOx, CO and HC emissions as gases pass through.

Fill Pipe Restrictor (FR) - prohibits the introduction of leaded fuel into the fuel tank.

Air Injection Systems (AIS) - draw filtered air in through the intake port and push air out the exhaust port.

Oxygen Sensor (O2s) - monitors the oxygen content of exhaust gases. It produces a voltage signal which is proportional to exhaust gas oxygen compared to outside oxygen.

Low voltage signal = lean mixture
High voltage signal = rich mixture

Computerized Engine Controls (CEC) - monitor and control a variety of engine/vehicle functions. CEC system is primarily an emission control system designed to maintain a 14.7:1 air/fuel ratio under most operating conditions.


High CO Readings High HC Readings
 A. Incorrect air fuel mixture  A. Defective points/electronic ignition
 B. Dirty air cleaner, choke or carb./fuel injection  B. Open plug wire or fouled spark plug
 C. Carburetor float level improperly adjusted  C. Vacuum leak
 D. Inoperative air pump  D. Incorrect air/fuel mixture
 E. Diluted lubricating oil  E. Inoperative air pump
 F. Soaked fuel evaporative canister  F. Incorrect ignition timing
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