SACRAMENTO, Calif. — The California Air Resources Board (CARB) will soon begin phasing in the On-Board Diagnostic (OBD) Monitor Readiness and Permanent Diagnostic Trouble Code (PDTC) requirements as part of Clean Truck Check.
An exact date has not been announced, but CARB officials state that it will be “in early 2024.”
“Readiness is determined by how many OBD system diagnostics have been completed and the number of vehicle operations since codes were cleared (OSC – Operation Since Clear),” a news release states. “The OBD system diagnostics are broken down into categories called ‘Monitors.’ Each Monitor must undergo diagnostic tests to determine whether those systems work correctly. The OBD system reports whether each Monitor has had time to complete its tests; if so, the Monitor is considered “Ready.”
Monitors’ specific numbers and types vary based on OBD protocol (J1939 vs. J1979), fuel type, vehicle make and model year. Based on the tests performed, most vehicles have all Monitors ready when compliance tests are submitted.
The OBD systems store information regarding vehicle operation since codes were cleared.
Most vehicles have OSC for one or more reasons:
- Warm-up cycles (WUCs) since clear
- Distance traveled, in km, since clear
- Engine run time, in minutes, since clear
Typically, vehicles can track WUCs in either minutes or distance since they are clear. The criteria will be applied to the OSC variables provided by an individual vehicle. As the requirements are phased in the thresholds for these variables will become more stringent over time.
Permanent diagnostic trouble codes (PDTCs) are very similar to regular diagnostic trouble codes (DTCs). The only difference is that they cannot be reset by disconnecting the vehicle’s battery or cleared using an OBD scan device like how regular DTCs can. The only way to clear a PDTC is to fix the underlying problem with the car that initially activated the PDTC, and then allow the vehicle sufficient drive time to re-run the Monitor that identified the problem in the first place. When the Monitor runs without identifying a problem, the PDTC will clear itself.
Things to do to have your best chance at passing the Clean Truck Check OBD test include:
- Getting your vehicle repaired as soon as your malfunction indicator lamp (right) is on, get your vehicle repaired as soon as possible
- Doing the OBD test early in the Clean Truck Check compliance window so you will have time to complete it if there are problems
- Avoid code clearing — OBD systems require substantial vehicle operation to complete their emission control diagnostic tests, and a vehicle that has not been operated enough or has too many monitors incomplete will fail the test
Code clearing can occur when:
- Disconnecting the battery
- Using an improperly installed kill switch that disconnects power to the OBD system [it is OK if the kill switch just cuts power to accessories/lights/etc.]
- Using an OBD scan device to clear codes
For more information, visit https://ww2.arb.ca.gov/obd-readiness-criteria.
Born and raised in Little Rock, AR, Erica N. Guy decided to stay in her hometown to begin her professional career in journalism. Since obtaining her bachelor’s degree from UAPB, Erica has professionally written for several publications about several topics ranging from lifestyle, tech, culture, and entertainment, just to name a few. Continuing her love for her hometown, she joined our team in June 2023, where she is currently a staff writer. Her career goals include continuing storytelling through her writing by being the best professional writer she can be. In her spare time, Erica enjoys trying new foods, cozying up with a good book, spending time with family and friends, and establishing herself as a future businesswoman.
