Modifying your 2016 Dodge Challenger or Charger Hellcat for enhanced performance is a thrilling endeavor. However, it often comes hand-in-hand with the appearance of OBD2 codes, particularly when exhaust systems are upgraded. Understanding these codes and how to address them is crucial to ensure your Hellcat runs smoothly and efficiently, without triggering unwanted check engine lights. This guide delves into common OBD2 code issues encountered after modifications like header installations and high-flow catalytic converters on your 2016 Hellcat, offering expert insights and solutions to keep your beast roaring without trouble codes.
Understanding O2 Sensor Codes After Header Installation
Installing aftermarket headers on your 2016 Hellcat can significantly alter the exhaust flow and temperature, impacting the readings of your oxygen (O2) sensors. A frequent issue arises with O2 transport delay, which is how quickly the O2 sensor readings are processed by the engine control unit (ECU). When headers are installed, the exhaust path changes, and the factory transport delay settings may no longer be accurate, leading to codes like P0133 (O2 Sensor Circuit Slow Response Bank 1 Sensor 1) or P0153 (O2 Sensor Circuit Slow Response Bank 2 Sensor 1).
Alt text: Location diagram of oxygen sensors on a vehicle exhaust system, highlighting upstream and downstream sensor positions for bank 1 and bank 2, crucial for understanding OBD2 code diagnostics related to sensor response times.
To remedy this, a common practice in tuning for modified vehicles is to adjust the O2 transport delay tables within the ECU. A recommended starting point, as per experienced tuners, is to increase these values by approximately 150%. This adjustment helps the ECU correctly interpret the O2 sensor signals after the header modification.
It’s tempting to simply disable or “turn off” these O2 sensor codes in the ECU. However, this approach is strongly discouraged. While you might be able to suppress the Malfunction Indicator Light (MIL) on your dashboard by unchecking the “Mil box” for these codes, the underlying issue remains. The O2 sensors become unsupported for emissions control, which can lead to problems with vehicle emissions compliance and potentially affect engine performance in the long run. Disabling the Service Engine Soon (SES) light but not the MIL box means the code will still be registered as a fault even if it’s not immediately visible on the dash.
Catalytic Converter Efficiency and High Flow Cats
Another area where OBD2 codes frequently surface after modifications is related to catalytic converter efficiency. Your 2016 Hellcat is equipped with catalytic converters to reduce harmful emissions. Factory catalytic converters are designed to be highly restrictive to maximize their efficiency in converting pollutants. Downstream O2 sensors, located after the catalytic converters, monitor their performance.
Alt text: Diagram illustrating the internal structure of a catalytic converter, showcasing the honeycomb matrix coated with catalyst materials, essential for understanding how exhaust gases are treated and why modifications can trigger OBD2 codes.
When comparing readings at idle between factory cats and high flow cats, significant differences emerge. With factory converters, downstream O2 sensors typically read in the 0.650-0.710 voltage range for each bank. This higher voltage indicates that the catalytic converter is effectively performing secondary combustion and reducing pollutants. In contrast, high flow catalytic converters, designed for less restriction and improved exhaust flow, will result in downstream O2 sensor readings in the 0.020-0.060 range. This lower reading is because high flow cats, while beneficial for performance, are less restrictive and thus less efficient at secondary combustion at idle compared to stock converters.
This difference in readings often triggers codes like P0420 (Catalyst System Efficiency Below Threshold Bank 1) or P0430 (Catalyst System Efficiency Below Threshold Bank 2). To address this when using high flow cats, the common solution is to employ O2 sensor defoulers on the downstream sensors.
Alt text: Image depicting the installation process of an O2 sensor defouler, showing how it spaces out the sensor from the direct exhaust stream to modify readings and prevent false OBD2 codes after catalytic converter modifications.
Defoulers physically space the O2 sensor out of the direct exhaust stream, effectively altering its readings to fall within acceptable ranges for the ECU. To prepare a defouler for a 2016 Hellcat, it’s recommended to drill out the opening with a 7/16 drill bit. Crucially, ensure you only enlarge the initial hole and not the smaller opening at the defouler’s tip, to avoid damaging the O2 sensor. This enlarged opening allows the larger Dodge O2 sensor to fit properly. For enhanced effectiveness, some enthusiasts add a small amount of steel wool from a kitchen cleaning pad into the defouler, packing it in to further filter the exhaust gases reaching the sensor.
Regarding code disabling in your tune, it’s generally safe to disable P0430 (Catalyst System Efficiency Below Threshold Bank 2) altogether without causing issues with catalyst support. However, disabling P0420 (Catalyst System Efficiency Below Threshold Bank 1) is not advisable as it can lead to the catalyst test becoming unsupported. Even if you use defoulers on both sides, it’s still recommended to leave P0420 enabled. This approach helps maintain rear closed-loop fueling and ensures fuel trims remain within acceptable parameters. Disabling rear closed-loop fueling or the catalytic converter test is also not recommended, as the cat test will be supported but never actually run, potentially masking real issues. Treating both banks similarly with defoulers helps keep fuel trims balanced and consistent across the engine.
Addressing Evaporative Emission (EVAP) System Codes
As a bonus tip for simplifying your emissions readiness, you can consider addressing EVAP system codes P0456 (Evaporative Emission System Leak Detected – Very Small Leak) and P0457 (Evaporative Emission System Leak Detected – Fuel Cap Off/Loose). In many vehicles, disabling these specific codes within the EVAP system settings can make the EVAP system readiness test complete almost instantly. While this trick has been reported to work on many car models, it may not be effective on all, as noted with a 2019 Charger Scat Pack. Experimentation may be necessary to see if this method works for your specific 2016 Hellcat.
Dealing with O2 Sensor Slow Response Codes
If you encounter O2 slow response codes, especially after modifications like long tube headers on older models (e.g., a 2009 Challenger, though less relevant for a 2016 Hellcat which would typically have shorter tube headers even when upgraded), the first step is to inspect the upstream O2 sensors for any physical damage. It is critical to emphasize that you should never cut and solder an O2 sensor cable. If an O2 sensor cable is damaged, the entire sensor should be replaced. If the sensor cable is too short due to modifications, use proper O2 sensor extenders to ensure a secure and reliable connection with a new sensor. Avoid dropping O2 sensors as they contain a delicate heater element made of glass, which can easily break.
Passing Emissions Testing
To ensure your 2016 Hellcat passes emissions testing after modifications, understanding the catalytic converter test parameters is helpful. Typically, the cat test runs when driving at a steady speed of 38 mph between 1350-1850 rpm, usually in 4th gear, for approximately 2 minutes. If the test is interrupted, simply resume the driving criteria when it is safe to do so. Alternatively, another method to complete the cat test, along with other readiness tests, is to cruise at 55 mph for about 8 minutes, then come to a complete stop and let the engine idle for 3 minutes. Finally, shut off the engine, turn the key back to the “on” position (without starting the engine), and the readiness tests should complete.
Double Defouling as a Last Resort
If you continue to experience persistent OBD2 code issues related to catalytic converter efficiency on bank 1 even after implementing the above solutions, and assuming your engine is running well mechanically, double defouling on bank 1 might be a necessary, albeit more complex, solution. This involves using two defoulers stacked together to further reduce the exhaust gases reaching the downstream O2 sensor on bank 1. However, ensure there is sufficient physical space to accommodate the double defouler setup without causing damage or interference.
By understanding these common OBD2 code issues and implementing the suggested solutions, you can effectively manage and resolve trouble codes on your modified 2016 Hellcat, ensuring optimal performance and emissions compliance. Remember to always prioritize accurate diagnostics and proper tuning adjustments over simply masking or disabling codes to maintain the longevity and health of your vehicle.
