The process of resetting OBDII codes often involves completing a specific driving cycle. This allows the vehicle’s onboard diagnostic system to monitor various components and ensure they are functioning correctly. For General Motors (GM) vehicles, understanding the specific steps of their OBDII driving cycle is crucial for a successful Obdii Code Reset.
The GM OBDII Driving Cycle: A Step-by-Step Guide
The GM driving cycle consists of eight distinct steps designed to test different aspects of the emission control system. Following these steps precisely is essential for accurate diagnostic results and effective OBDII code reset.
1. Cold Start Initiation
The driving cycle begins with a cold start, meaning the engine coolant temperature must be below 122°F (50°C) and within 11°F (6°C) of the surrounding air temperature. Avoid leaving the key in the ignition before starting to ensure the heated oxygen sensor diagnostic runs properly. This initial step is vital for a comprehensive OBDII code reset.
2. Idle Period with Load
After the cold start, let the engine idle for two and a half minutes with the air conditioner and rear defroster turned on. Applying additional electrical loads helps test components like the O2 heater, passive air system, and purge system for “no flow” conditions. This stage also monitors misfires and fuel trim if the system enters closed-loop operation. This idle period is crucial for comprehensive diagnostics and potential OBDII code reset.
3. Acceleration Phase One
Next, turn off the air conditioner and all other loads. Accelerate at half throttle until reaching 55 mph (88 km/h). This phase engages diagnostics for misfires, fuel trim, and purge flow. Proper acceleration is key for accurate system evaluation and OBDII code reset.
4. Maintaining Steady Speed One
Hold a constant speed of 55 mph (88 km/h) for three minutes. This allows the system to monitor oxygen sensor response, air intrusion, EGR system functionality, purge system, misfires, and fuel trim. Maintaining a steady speed is essential for this diagnostic phase and for a complete OBDII code reset.
5. Deceleration Phase One
Decelerate without using the brakes, clutch, or shifting gears. Allow the vehicle to coast down to 20 mph (32 km/h). This tests the EGR system, purge system, and fuel trim. Controlled deceleration is important for accurate results and a successful OBDII code reset.
6. Acceleration Phase Two
Accelerate again, this time using 3/4 throttle to reach 55-60 mph (88-96 km/h). This phase mirrors the diagnostics performed in step 3, further evaluating misfires, fuel trim, and purge flow, contributing to a comprehensive OBDII code reset process.
7. Maintaining Steady Speed Two
Maintain a steady speed of 55 mph (88 km/h) for five minutes. This extended period enables the system to thoroughly assess the catalytic converter’s performance, in addition to the components monitored in step 4. This phase is crucial for catalyst monitoring and can influence OBDII code reset outcomes.
8. Deceleration Phase Two
Finally, decelerate as in step 5, allowing the vehicle to coast down to 20 mph (32 km/h) without using the brakes, clutch, or shifting gears. This final deceleration provides a last check of the EGR, purge, and fuel trim systems, finalizing the data collection for OBDII code reset.
This comprehensive GM driving cycle enables the vehicle’s OBDII system to perform a complete diagnostic evaluation, leading to a more accurate and effective OBDII code reset. By understanding and adhering to each step, you ensure a more reliable diagnostic process.
