California has strict smog laws, and understanding how your vehicle’s On-Board Diagnostics (OBD) system interacts with these regulations is crucial for passing a Smog Check. This article outlines the pass/fail standards for the OBD test portion of a Smog Check, focusing on readiness monitors, diagnostic trouble codes (DTCs), communication protocols, and specific vehicle issues that might affect your vehicle’s compliance with California’s evolving smog laws.
Understanding OBD2 Readiness Monitors and California Smog Checks
Your vehicle’s OBD2 system continuously monitors emission control components. These self-tests, known as readiness monitors, ensure your car runs cleanly. California Smog Checks assess these monitors to determine if your vehicle meets emission standards. Incomplete monitors can lead to a failed Smog Check, even without a Check Engine Light. While regular driving often sets these monitors, some require specific driving conditions.
A standard OBD2 port in a vehicle.
OBD2 Pass/Fail Standards for California Smog Checks
California’s Bureau of Automotive Repair (BAR) defines specific criteria for passing the OBD portion of a Smog Check. These standards vary by model year and fuel type and cover several key areas:
Readiness Monitor Completion
The number of allowed incomplete readiness monitors depends on your vehicle’s year and fuel type:
- 1996-1999 Gasoline Vehicles: Any one incomplete monitor is permissible.
- 2000 and Newer Gasoline Vehicles: Only the evaporative system monitor can be incomplete.
- 1998-2006 Diesel Vehicles: All monitors must be complete.
- 2007 and Newer Diesel Vehicles: Only the Particulate Filter and Non-Methane HydroCarbon (NMHC) monitors can be incomplete.
Malfunction Indicator Lamp (MIL) Status
The MIL, often called the Check Engine Light, must function correctly:
- Pass: The MIL illuminates when the ignition is on and the engine is off (KOEO) and turns off when the engine is running (KOER).
- Fail: The MIL does not illuminate during KOEO or stays illuminated during KOER.
Communication Protocols
The OBD2 system must communicate correctly with the Smog Check equipment:
- BAR-97 Test: The vehicle must communicate with the BAR-97 emissions inspection system.
- On-Board Diagnostic Inspection System (OIS) Test: The vehicle must communicate with the OIS and transmit required data, including MIL status, DTCs, and monitor status.
Permanent Diagnostic Trouble Codes (PDTCs)
For 2010 and newer vehicles, the presence of a PDTC, which indicates a persistent emission-related fault, results in a Smog Check failure. However, BAR acknowledges certain vehicles have issues clearing specific PDTCs and is working with the California Air Resources Board (CARB) to address these concerns. Some manufacturers offer extended warranties or recalls for vehicles with PDTC issues.
An illuminated Check Engine Light can indicate various issues, including emission-related problems.
Modified Software
Vehicles with illegally modified software will fail the Smog Check. Software approved by CARB through an Executive Order is acceptable.
Addressing Common OBD2 Issues in California
Specific makes and models have known issues affecting OBD2 Smog Check results. These range from communication problems to incomplete monitors and false MIL illumination. The BAR provides guidance for handling these issues, often involving software updates, repairs, or specific drive cycles. Consult Section D of the original document for a detailed list of affected vehicles and recommended solutions. For some vehicles, BAR-OIS has been programmed to accommodate these anomalies.
Conclusion
Navigating California’s smog laws requires understanding your vehicle’s OBD2 system and its compliance with state regulations. By staying informed about readiness monitors, DTCs, communication protocols, and potential vehicle-specific issues, you can increase your chances of passing a Smog Check. If you encounter persistent problems, consult a qualified automotive technician or a Smog Check Referee. Staying up-to-date with California’s changing smog laws and maintaining your vehicle’s emission system will ensure a smoother Smog Check experience.
