How to become a Clean Truck Check Credentialed Tester Contacto Clean Truck Check (HD I/M) Correo electrónico hdim@arb.ca.gov Teléfono (866) 634-3735 This webpage will instruct you on the steps to become a Clean Truck Check Credentialed tester. Each image is clickable with a link that will take you to the appropriate website for that action. Step 1Step 2Step 3Step 4Step 5 Additional Resources- Learn More