Experiencing issues with your Honda failing a smog test due to unset readiness monitors? This comprehensive guide explains the Honda Obdii Drive Cycle, a procedure designed to set these monitors and ensure your vehicle passes inspection. The OBD-II drive cycle is initiated from a cold start, which is defined as a coolant temperature below 122 degrees Fahrenheit (50 degrees Celsius) and with the coolant and air temperature sensors reading within 11 degrees Fahrenheit (6 degrees Celsius) of each other.
Important Cold Start Note: Ensure the ignition key remains off prior to initiating the cold start. Turning the key to the ‘on’ position beforehand may prevent the heated oxygen sensor diagnostic from running correctly.
Here’s a step-by-step breakdown of the Honda OBDII drive cycle:
Step 1: Initial Idle (2.5 minutes)
- Start the engine and let it idle in drive for two and a half minutes (150 seconds).
- During this step, engage both the air conditioning (A/C) and rear defrost at maximum settings.
- OBD-II System Checks: This initial idle period allows the OBD-II system to perform checks on crucial components, including:
- Oxygen sensor heater circuits
- Air pump system (if equipped)
- EVAP (Evaporative Emission Control System) purge function
Step 2: Acceleration and Steady Speed (3 minutes at 55 mph)
- Turn off the A/C and rear defrost.
- Accelerate smoothly to 55 mph (88 km/h) using approximately half throttle.
- Maintain a steady speed of 55 mph for three minutes.
- OBD-II System Checks: This phase focuses on:
- Ignition misfire detection
- Fuel trim adjustments
- Canister purge system operation
- EGR (Exhaust Gas Recirculation) system monitoring
- Air pump system (if equipped)
- Oxygen sensor performance
- Continued canister purge monitoring
Step 3: Deceleration (Coast Down to 20 mph)
- Safely decelerate or coast down to 20 mph (32 km/h) without applying the brakes or depressing the clutch (for manual transmissions).
- OBD-II System Checks: During deceleration, the system checks:
- EGR system functionality
- Canister purge functions
Step 4: Re-acceleration to Higher Speed (55-60 mph)
- Accelerate again to a speed between 55 to 60 mph (88-96 km/h) using half throttle.
- OBD-II System Checks: Similar to Step 2, this acceleration phase re-evaluates:
- Ignition misfire
- Fuel trim
- Canister purge system
Step 5: Extended Steady Speed (5 minutes at 55-60 mph)
- Maintain a steady speed between 55 to 60 mph for five minutes.
- OBD-II System Checks: This extended period allows for thorough monitoring of:
- Catalytic converter efficiency
- Misfire detection
- EGR system operation
- Fuel trim accuracy
- Oxygen sensor performance
- Canister purge system functions
Step 6: Final Deceleration and Stop
- Decelerate or coast down to a complete stop without using the brakes.
- OBD-II System Checks: This final coast down allows for a last check of:
- EGR system
- Canister purge system
By diligently following these steps for your Honda OBDII drive cycle, you provide the necessary conditions for your vehicle’s onboard diagnostic system to run comprehensive tests and set the readiness monitors. Completing this drive cycle can often resolve issues preventing your Honda from passing emissions testing, getting you back on the road legally and efficiently. Remember to consult your Honda owner’s manual or a qualified technician for specific instructions related to your vehicle model if needed.
