Permanent DTC / Smog Checks in CA

As of July 1, 2019, vehicles with Permanent DTCs will fail a smog check. Permanent DTCs were phased-in with 2010 model year vehicles and was completed for 2012 model year

What are Permanent Diagnostic Trouble Codes?

Permanent Diagnostic Trouble Codes (PDTCs) are very similar to regular Diagnostic Trouble Codes (DTCs). However, unlike regular DTCs, they cannot be reset by disconnecting the vehicle’s battery or cleared using an On-Board Diagnostic (OBD) scan tool. The only way to clear a PDTC is to fix the underlying problem with the vehicle that originally caused the PDTC and its corresponding DTC to set, 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.

Are there circumstances under which a PDTC will not cause a vehicle to fail a Smog Check inspection?

Yes. PDTCs will be ignored if the vehicle has completed at least 15 warm-up cycles and been driven at least 200 miles since its OBD information was last cleared.

Conclusion

Permanent DTCs can cause a vehicle to fail a smog check even if the check engine light (MIL) is not illuminated. Unplugging the vehicle’s battery or using a scan tool are techniques sometimes used to clear OBD information for a vehicle that has an illuminated malfunction indicator light in an attempt to hide the fact that the vehicle is malfunctioning. Some of these vehicles can pass a Smog Check inspection before the vehicle can re-identify the underlying problem that set the malfunction indicator light and DTC(s). This can have a dramatic impact on air quality and decrease the effectiveness of the Smog Check Program. Although the use of readiness monitors reduces the chances of passing a Smog Check inspection with an active DTC, PDTCs can further ensure emission control systems are working correctly.

At JUST SMOGS®+ REPAIR, we specialize in emission related diagnosis and repair. If your check engine light is on or your vehicle has failed a smog check, feel free to give us a call: 714-596-1019.