FAQs: ASM/TSI Emissions Testing

ASM/TSI Testing

• What is ASM testing?
• What is TSI testing?

Understanding Tailpipe Failures

• Reasons your vehicle may have failed the ASM/TSI Test
• HC Diagnosis
• CO Diagnosis
• NOX Diagnosis

ASM Emissions Test
What is ASM2 and how does it work?
This test uses a dynamometer, which measures emissions under simulated driving conditions. In a sense, it's like a treadmill stress test for your vehicle. This tailpipe test is a cost-effective way to get very accurate, realistic results. A vehicle will fail the test if there is an excessive amount of Hydrocarbon, Carbon Monoxide or Oxides of Nitrogen.

Please note that 4 wheel drive vehicles will continue to receive the current Two-Speed Idle test. If your vehicle fails the ASM test, you can return to the same public inspection station within 15 days of your initial test for a free retest.

Two Speed Idle Test
The Two-Speed Idle test is a tailpipe emissions test. This means the analyzer measures exhaust emissions directly from the vehicle's tailpipe with the engine idling at a high and then low speed. TSI measures most of the common factors contributing to the formation of lung damaging ground level ozone.

A vehicle will fail the test if there are excessive amounts of hydrocarbons or carbon monoxide. TSI is used for older vehicles that are not equipped with the advanced on-board diagnostic computer system.

A Few 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. Check the following:

• Internal Engine Problems
• Faulty Air Pump
• Ignition System
• Exhaust Gas Recirculation 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. Check the following:

• 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.
Check the following:

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

Diagnostics for NOx failures

OVERALL
Check for causes of high combustion temperatures. Primary systems that affect NOx include:

• Mixture control (lean)
• EGR
• Ignition
• Check Catalytic Converter

1981-86
Check the following:

• O2 sensor (The signal from the O2 Sensor provides a wealth of information on how the vehicle is running.)
• EGR valve and EGR hose
• Ignition timing and system (advanced timing and ignition components are some of the most common problems)
• Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)
• Catalytic converter
• Primary feedback sensor failure, including oxygen sensor, MAP/MAF, TPS, RPM, and CTS sensors

1987-95
Check the following:

• Use OBD, if available
• O2 sensor
• EGR valve and EGR hose
• Ignition timing and system (advanced timing and ignition components are some of the most common problems)
• Primary feedback sensor failure including, oxygen sensor, MAP/MAF, TPS, RPM, and CTS sensors
• Vacuum lines
• Catalytic converter

Diagnostics for HC failures

OVERALL

• Check for cause of rich mixture, e.g. Oxygen Sensor
• Check carburetor if equipped
• Ignition timing and system (advanced timing and ignition components are some of the most common problems)
• Check lines and hoses
• Check catalytic converter

1981-86
Check the following:

• Carburetor
• O2 sensor
• Ignition timing and system (advanced timing and ignition components are some of the most common problems)
• Catalytic converter
• Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)
• Primary feedback sensor failure including MAP/MAF, TPS, RPM, and CTS sensors

1987-95
Check the following:

• Use OBD, if available
• O2 sensor
• Ignition timing (advanced timing and ignition components are some of the most common problems)
• Catalytic converter
• Primary feedback sensor failure including MAP/MAF, TPS, RPM, and CTS sensors.
• Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)

Diagnostics for CO failures

OVERALL
Check for cause of rich mixture, e.g. Oxygen Sensor

• Check carburetor if equipped
• Check lines and hoses
• Check catalytic converter

1981-86
Check the following:

• Carburetor
• O2 sensor
• Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)
• Primary feedback sensor failure including MAP/MAF, TPS, RPM, and CTS sensors
• Catalytic converter

1987-95
Check the following:

• Use OBD, if available
• O2 sensor
• Fuel Injectors/Carburetors
• Primary feedback sensor failure including MAP/MAF, TPS, RPM, and CTS sensors
• Vacuum lines (deterioration of vacuum lines, inlet manifold seals become more prevalent causes with age)