Skip to Main Content


Common Emission Control System (ECS) Abbreviations

Component Name Abbreviation
Exhaust Gas Recirculation EGR
Cooled EGR EGR-C
Charge Air Cooler CAC
Diesel Oxidation Catalyst DOC
Engine/Powertrain Control Module ECM/PCM
Throttle body fuel injection TBI
Indirect/Direct Diesel Injection IDI/DDI
Sequential/multi port injection SFI/MFI
Diesel Particulate Filter DPF
Periodic Trap Oxidizer PTOX
Turbocharger/Supercharger TC/SC
Heated/Oxygen Sensor HO2S/02S
Three-way/Oxidizing Catalyst TWC/OC
Pulsed/Secondary Air Injection PAIR/AIR
Smoke Puff Injector SPL
Ammonia Oxidation Catalyst AMOX
Selective Catalyst Reduction-Urea SCR-U
SCR-Ammonia SCR-N
Engine Modification EM



The California Air Resources Board is Beginning to Roll out the Clean Truck Check

What is Clean Truck Check?

Passenger vehicles and lighter trucks have been required to undergo periodic emissions testing and reporting for decades through the Bureau of Automotive Repair’s Smog Check Program. Now under the California Air Resources Board’s (CARB) Clean Truck Check, big trucks and other heavy-duty vehicles traveling on California’s roadways will be subject to similar requirements to ensure polluting, poorly maintained heavy-duty vehicles operating in California are quickly identified and repaired. The Clean Truck Check will provide significant reductions in smog-forming and carcinogenic toxic air pollution necessary to achieve federal air quality mandates and healthy air in California’s communities.

What Type of Vehicles are Subject to the Clean Truck Check?

Nearly all diesel and alternative fuel heavy-duty trucks and buses with a gross vehicle weight rating (GVWR) over 14,000 pounds that operate in California are subject to the Clean Truck Check. This includes hybrid trucks and buses, commercial vehicles, privately-owned vehicles, motorhomes, government vehicles, and vehicles registered outside of California.

When Does the Clean Truck Check Start?

The first phase of the Clean Truck Check implementation began in January 2023 with the use of roadside emissions monitoring devices (REMD) to screen for vehicles that may have high emissions. Vehicles flagged as potential high emitters may be required to undergo follow-up vehicle compliance testing to ensure they are operating with properly functioning emissions control systems. When fully implemented in the 2024 timeframe, the Clean Truck Check will require most heavy-duty vehicles operating in California (including out-of-state vehicles) to undergo twice per year periodic compliance testing.

Who Can Perform Clean Truck Check Compliance Testing?

Clean Truck Check compliance testing must be performed by a credentialed tester who has completed the CARB’s free, online Tester Training Course available at Tester Training Course and Exam | California Air Resources Board and passed the accompanying examination.

Where Do I Get Additional Clean Truck Check Information?

For more information on CARB’s Clean Truck Check, go to: Clean Truck Check | California Air Resources Board