FAQs: ASM/TSI Emissions Testing
ASM/TSI Testing
- What is ASM testing?
- What is TSI testing?
Understanding Tailpipe Failures
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)