What is ASM2?

ASM2, or Accelerated Simulation Mode 2, addresses problems the old two-speed idle tailpipe emissions analyzer. First, the two-speed idle tailpipe analyzer does not test the vehicle for emissions while under load and acceleration as expected under normal operation. Second, since it only tests for carbon monoxide and hydrocarbons, oxides of nitrogen (NOx) go undetected. Nox has been determined to be a major contributing factor in the formation of ground level ozone.

The ASM2 test requires the vehicle to be driven on a dynamometer, which puts a load on the vehicle to simulate normal driving conditions. The three main exhaust pollutants measured are hydrocarbons, carbon monoxide and oxides of nitrogen (NOx). If there is an excessive amount of any of these pollutants, a vehicle will fail the emissions test.

Reasons why a vehicle may fail the ASM2 test:

Excessive Hydrocarbons (HC): High hydrocarbon emissions result when fuel in the engine does not burn completely. HC in the presence of oxides of nitrogen (NOx) and sunlight may form ground-level ozone, a major component of urban smog. Possible factors are:

• Internal Engine Problems
• Faulty Air Pump
• Ignition System
• Exhaust Gas Re-circulation System (EGR)
• Catalytic Converter
• Gas Cap

Excessive Carbon Monoxide (CO): A rich fuel mixture can cause high amounts of carbon monoxide, which can occur when there is too much or too little air reaching the combustion chamber. Possible factors are:

• Misadjusted Carburetor
• Faulty Fuel Injection System
• Worn Rings/Valve Guides
• Air Pump System

Excessive Oxides of Nitrogen (NOx): High NOx can occur when there is excessive temperature in the combustion chamber or a damaged catalytic converter. Possible factors are:

• Air Injection System
• Exhaust Gas Re-circulation System (EGR)
• Combustion Chamber Deposits
• Oxygen Sensor
• Catalytic Converter