Experiencing issues with your Honda failing an emissions test due to incomplete readiness monitors? This is a common problem, often occurring after battery disconnection or recent car repairs. The solution might be simpler than you think: performing an OBD2 drive cycle. This article, tailored for Honda vehicles, will guide you through the process, helping you understand and execute the necessary steps to reset your car’s computer and get those monitors ready for a smog check.
Understanding the Honda OBD2 Drive Cycle
The On-Board Diagnostics II (OBD2) system in your Honda constantly monitors various engine and emission control systems. Readiness monitors are a part of this system, designed to confirm that these systems are functioning correctly. When these monitors are not in a “ready” state, your vehicle might fail an emissions test, even if there isn’t a major issue. A Honda OBD2 drive cycle is a specific series of driving conditions that allows your car’s computer to run self-tests and set these monitors to “ready”.
This drive cycle should be initiated from a cold start. A cold start is defined as the engine coolant temperature being below 122 degrees Fahrenheit (50 degrees Celsius) and the air and coolant temperature sensors reading within 11 degrees Fahrenheit (6 degrees Celsius) of each other.
Important Note: Ensure the ignition key is not turned to the “ON” position before initiating the cold start. Doing so may prevent the heated oxygen sensor diagnostic from running properly.
Here are the steps to perform an OBD2 drive cycle on your Honda:
Step 1: Initial Idle
As soon as you start the engine from a cold start, allow it to idle in drive for two and a half minutes (150 seconds). Ensure the air conditioning (A/C) and rear defroster are turned on during this step. This initial idling period allows the OBD2 system to check the oxygen sensor heater circuits, air pump, and EVAP (Evaporative Emission Control System) purge functions.
Step 2: Acceleration and Steady Speed (55 mph)
Turn off the A/C and rear defroster. Gently accelerate to 55 mph (88 km/h) using approximately half throttle. Maintain a steady speed of 55 mph for three minutes. During this phase, the OBD2 system will monitor for ignition misfires, fuel trim adjustments, and canister purge operations. It also checks the EGR (Exhaust Gas Recirculation) system, air pump, oxygen sensors, and canister purge system again.
Step 3: Deceleration
Safely decelerate (coast down) from 55 mph to 20 mph (32 km/h) without applying the brakes or depressing the clutch pedal. This step enables the OBD2 system to evaluate the EGR and purge functions during deceleration.
Step 4: Re-acceleration and Steady Speed (55-60 mph)
Accelerate again to a speed between 55 to 60 mph (88-96 km/h) using half throttle. Hold this steady speed for five minutes. This stage allows the OBD2 system to re-check for misfires, fuel trim, and purge system efficiency.
Step 5: Final Deceleration to Stop
Finally, decelerate (coast down) to a complete stop without using the brakes. During this final coast down, the OBD2 system performs a last check of the EGR system and canister purge functions.
After completing these steps, turn off the ignition and use an OBD2 scanner to check if your Honda’s readiness monitors have been reset. You may need to repeat the drive cycle if some monitors are still not ready.
Disclaimer: This drive cycle is a general guideline and might need slight variations depending on your specific Honda model and year. Always consult your Honda owner’s manual or a trusted repair manual for the most accurate procedure for your vehicle. If you continue to experience issues with readiness monitors, it’s recommended to seek professional diagnosis from a certified mechanic.
