Everything you need to know about CARB Clean Truck Check compliance. Can't find your answer? Call or text us at (661) 241-8076.
General
About the Clean Truck Check
Under CARB's Clean Truck Check (CTC), heavy-duty trucks and buses traveling California roads are subject to periodic emissions testing — similar to the Smog Check program for passenger vehicles. The program identifies poorly maintained, high-emitting vehicles and ensures they are repaired, reducing smog-forming and toxic air pollution across California.
Nearly all diesel and alternative fuel heavy-duty trucks and buses with a GVWR over 14,000 lbs operating in California must comply. This includes hybrid trucks, commercial vehicles, privately-owned vehicles, motorhomes, government vehicles, and out-of-state vehicles operating in California.
Blue Sky Smog handles the testing and CARB submission — and we'll help you set up your account for free.
The first phase began in January 2023 with roadside emissions monitoring devices screening for high-emitting vehicles. When fully implemented, most heavy-duty vehicles operating in California must undergo twice-yearly periodic compliance testing. Don't wait — deadlines are staggered by model year and enforcement is ongoing.
OBD Testing
Technical Questions
For a vehicle to pass OBD testing, no DTCs or Permanent DTCs (PDTCs) may be present, and the vehicle must meet at least one of the following criteria since codes were last cleared:
At least 5 warm-up cycles (WUC), or
At least 200 miles traveled, or
At least 400 minutes engine run time, or
At most 2 incomplete OBD monitors
If a PDTC is present, it will be ignored if the vehicle meets at least one of these criteria since codes were last cleared:
At least 15 WUC, or
At least 400 miles traveled, or
At least 800 minutes engine run time, or
At most 1 incomplete OBD monitor
Note: meeting any one of these criteria is sufficient — incomplete monitors alone do not cause a failure if another criterion is met.
A warm-up cycle means driving the vehicle until engine coolant temperature rises by at least 40°F after startup and reaches at least 140°F for diesel engines (160°F for natural gas engines).
PDTCs are similar to regular DTCs but cannot be cleared by disconnecting the battery or using a scan tool. The only way to clear a PDTC is to fix the underlying issue, then allow sufficient drive time for the relevant monitor to re-run without finding a problem — at which point it clears itself automatically.
A "Not Ready" result means the vehicle did not meet any of the OBD readiness criteria at the time of testing. This is not the same as incomplete monitors — if the vehicle meets any one of the other criteria (enough miles, engine run time, or warm-up cycles), incomplete monitors alone won't cause a Not Ready result. If your vehicle does receive a Not Ready result, continue driving it under normal operating conditions for a few days to accumulate more drive cycles, then have it retested. There is no charge if the vehicle does not pass — that's our No Pass, No Pay guarantee.
Yes — please ensure your check engine light is not illuminated before scheduling a test. An active check engine light typically indicates an active DTC which will result in a failed test. If your light is on, have the issue diagnosed and repaired first, then allow sufficient drive cycles before testing.
Still Have Questions?
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