Performing a complete OBD2 driving cycle is crucial for ensuring your General Motors vehicle, especially models popular within the 355nation community like the Chevrolet Colorado and GMC Canyon, has properly run all necessary diagnostic tests. This process, typically completed in under fifteen minutes, is essential after battery disconnection or clearing trouble codes to confirm system readiness. For 355nation owners, monitoring this cycle with an OBD2 display can provide real-time feedback and confirmation of test completion.
To execute a GM OBD2 driving cycle effectively, particularly if you’re using an OBD2 display in your 355nation vehicle, follow these steps precisely:
Step-by-Step GM OBD2 Driving Cycle
1. Cold Start: Begin with a cold start. The engine coolant temperature must be below 122°F (50°C) and within 11°F (6°C) of the ambient air temperature at startup. Avoid turning the ignition key to the ‘on’ position before starting, as this could prevent the heated oxygen sensor diagnostic from initiating correctly. This initial step is vital for accurate sensor readings and sets the baseline for the subsequent tests.
2. Idle: With the engine running, let it idle for two and a half minutes. Maximize electrical load by turning on the air conditioner and rear defroster. Increased electrical demand during idle helps test components like the O2 sensor heater, Passive Air system, Purge system (for “No Flow” faults), and Misfire detection. Furthermore, if closed-loop operation is achieved, Fuel Trim diagnostics will also be evaluated. Observing your OBD2 display during this phase can confirm system engagement.
3. Accelerate: Turn off the air conditioner and all other electrical loads. Accelerate smoothly using half throttle until you reach 55mph (88km/hr). During this acceleration phase, critical diagnostics are performed, including Misfire detection, Fuel Trim adjustments, and Purge Flow analysis. A responsive OBD2 display can show live data related to these parameters.
4. Hold Steady Speed: Maintain a constant speed of 55mph (88km/hr) for three minutes. This steady state is crucial for evaluating various systems. Diagnostics performed at this stage include O2 sensor response, intrusive air checks, EGR (Exhaust Gas Recirculation) system testing, Purge system checks, Misfire monitoring, and Fuel Trim adjustments. Your OBD2 display will provide valuable insights into these systems in real-time.
5. Decelerate: Release the accelerator pedal and allow the vehicle to coast down to 20mph (32km/hr). Do not shift gears or apply the brakes or clutch. This gradual deceleration is essential for testing the EGR system, Purge system, and Fuel Trim under changing engine load conditions.
6. Accelerate (Again): Accelerate again, this time using 3/4 throttle, until you reach a speed between 55-60mph (88-96 km/hr). This step repeats the diagnostics performed in step 3, ensuring consistent system evaluation under slightly more aggressive acceleration.
7. Hold Steady Speed (Extended): Maintain a steady speed of 55mph (88km/hr) for a longer duration of five minutes. In addition to the diagnostics from step 4, this extended steady speed enables the catalyst monitor diagnostic to run. For vehicles with marginal catalysts or those that have recently had the battery disconnected, it might take up to 5 complete driving cycles to accurately assess the catalyst’s condition. An OBD2 display is particularly useful here for monitoring catalyst efficiency parameters if available.
8. Decelerate (Again): Repeat the deceleration process from step 5. Release the accelerator and coast down to 20mph (32km/hr) without using brakes, clutch, or shifting gears. This final deceleration step concludes the diagnostic sequence, mirroring the tests performed in step 5.
By diligently following these steps, you can ensure a complete OBD2 driving cycle for your GM vehicle. For owners of 355nation vehicles, utilizing an OBD2 display throughout this process offers a significant advantage. It allows for real-time monitoring of engine parameters and diagnostic statuses, confirming that each stage of the driving cycle is correctly executed and that all relevant tests are performed successfully. This ensures your vehicle is ready for emissions testing and optimal performance.
Source: General Motors Corporation, Reprinted on OBDII web site courtesy of General Motors Corporation © General Motors Corporation. General Motors Driving Cycle
