This guide provides information on On-Board Diagnostic (OBD) testing for 2020 Peterbilt trucks, focusing on passing California’s Smog Check inspection. We’ll cover pass/fail standards and address common issues encountered during the OBD test.
Understanding OBD Readiness Monitors for 2020 Peterbilt
OBD readiness monitors are self-diagnostic tests run by your truck’s computer to ensure the emission control system is functioning correctly. These monitors need to complete successfully for your Peterbilt to pass the OBD portion of the Smog Check. While normal driving usually allows these monitors to run, certain driving conditions or infrequent use can hinder their completion.
For 2020 and newer diesel vehicles, like your Peterbilt, only the Particulate Filter and Non-Methane HydroCarbon (NMHC) monitors are allowed to be incomplete to pass the OBD test. This standard was implemented on July 5, 2023.
Malfunction Indicator Lamp (MIL) Inspection
The MIL, also known as the “Check Engine” light, is another crucial aspect of the OBD test. During the inspection:
- Key On Engine Off (KOEO): The MIL should illuminate.
- Key On Engine Running (KOER): The MIL should turn off.
A malfunctioning MIL, such as failure to illuminate when the key is on and the engine is off, will result in an automatic failure of the OBD test.
OBD Communication and Your 2020 Peterbilt
Establishing communication between the OBD system and the testing equipment is paramount. Common reasons for communication failures include:
- Damaged OBD connector or wiring
- Aftermarket equipment interfering with the system
- Invalid data transmission from the vehicle’s computer
Ensure the OBD connector is in good condition and free of debris before the inspection. Consult a qualified technician if you suspect wiring issues or interference from aftermarket components.
Permanent Diagnostic Trouble Codes (PDTCs)
Since July 1, 2019, the Smog Check inspection includes a PDTC check. PDTCs act like regular Diagnostic Trouble Codes (DTCs) but can’t be erased by simply clearing the codes or disconnecting the battery. They only clear after the OBD system confirms the issue is resolved.
For 2010 and newer vehicles:
- A stored PDTC will cause the vehicle to fail, regardless of the MIL status.
- PDTCs are ignored if the vehicle has driven at least 200 miles and completed 15 warm-up cycles since the last OBD information clear.
Some vehicles have known issues clearing specific PDTCs. If your 2020 Peterbilt fails due to a PDTC, consult your dealer, as there might be recalls, extended warranties, or repair campaigns to address the issue.
Modified Software and Smog Check Compliance
As of July 19, 2021, a check for modified software was added to the Smog Check. Software modifications not approved by the California Air Resources Board (CARB) will result in a failed inspection. If your Peterbilt has modified software, ensure it has a valid CARB Executive Order. Otherwise, you’ll need to restore the original OEM software to pass the inspection.
Common OBD Issues in Similar Heavy-Duty Trucks
While specific OBD issues for the 2020 Peterbilt aren’t explicitly listed in the source document, similar heavy-duty trucks from this era often experience problems with:
- Exhaust Gas Sensor (EGS) Monitor: This monitor might not complete due to factors like recent Diesel Particulate Filter (DPF) regeneration or sensor malfunctions.
- NOx Aftertreatment System Monitor: Issues with the Selective Catalytic Reduction (SCR) system, Diesel Exhaust Fluid (DEF) quality or level, or related sensors can prevent this monitor from completing.
Addressing OBD Issues in Your 2020 Peterbilt
Before your Smog Check, consider these steps:
- Consult your Peterbilt dealer: They can diagnose specific OBD issues and inform you about any applicable recalls or software updates.
- Check for Technical Service Bulletins (TSBs): Peterbilt releases TSBs to address known issues. A relevant TSB might offer a solution to your specific problem.
- Use a professional-grade OBD2 scanner: These scanners provide more detailed diagnostic information than generic code readers, helping pinpoint the root cause of a problem.
Conclusion
Passing the Smog Check is essential for operating your 2020 Peterbilt legally in California. Understanding the OBD test requirements and addressing potential issues proactively will increase your chances of a successful inspection. Consult your dealer or a qualified technician if you encounter persistent OBD problems.
