Are you having trouble getting your 1999 Honda Accord to pass a smog check because the OBD2 system’s readiness monitors are not set? You’re not alone. Many owners of older vehicles, like the ’99 Accord, encounter this issue. The On-Board Diagnostics II (OBD2) system in your Honda needs to complete a self-test, and sometimes, it requires a specific driving pattern known as a “drive cycle” to set all the monitors to “ready.” This article will guide you through the OBD2 drive cycle for your 1999 Honda Accord, ensuring your car is prepped for its emissions test.
The OBD2 drive cycle is essentially a series of driving maneuvers designed to allow your car’s computer to run diagnostics on various emission control systems. For a 1999 Honda Accord, completing this cycle can be crucial for setting the readiness monitors, which are indicators that these tests have been performed. If these monitors aren’t ready, your vehicle might fail a smog test, even if there are no underlying emission problems.
This drive cycle is based on standard OBD2 protocols but is tailored for vehicles like your 1999 Honda Accord. It’s important to follow these steps precisely for the best chance of success.
Here’s how to perform the OBD2 drive cycle on your 1999 Honda Accord:
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Cold Start Conditions: Begin with a cold start. This means the engine coolant temperature must be below 122 degrees Fahrenheit (50 degrees Celsius), and the air temperature and coolant temperature sensors should be within 11 degrees Fahrenheit (6 degrees Celsius) of each other. Crucially, ensure the ignition key is NOT turned on before this cold start. Turning the key to the ‘on’ position prematurely can prevent the heated oxygen sensor diagnostic from running properly.
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Initial Idle: Once the engine is started, let it idle in drive for two and a half minutes (150 seconds). During this step, turn on the air conditioning (A/C) and the rear defroster to increase the engine load. This idle period allows the OBD2 system to check the oxygen sensor heater circuits, the air pump (if equipped), and the EVAP (Evaporative Emission Control) purge system.
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Warm Idle and Acceleration: Turn off the A/C and rear defroster. Now, accelerate smoothly to 55 mph (88 km/h) using about half throttle. This acceleration phase allows the OBD2 system to check for ignition misfires, monitor fuel trim (adjustments to the air-fuel mixture), and test the canister purge system.
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Steady Speed – Part 1: Maintain a steady speed of 55 mph (88 km/h) for three minutes. During this constant speed phase, the OBD2 system monitors the Exhaust Gas Recirculation (EGR) system, the air pump (if applicable), the oxygen sensors, and the canister purge system again.
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Deceleration: Safely decelerate (coast down) from 55 mph to 20 mph (32 km/h) without using the brakes or depressing the clutch (for manual transmissions). This coasting down allows the OBD2 system to check the EGR system and purge functions under deceleration conditions.
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Re-acceleration: Accelerate again to 55 to 60 mph (88-96 km/h) using half throttle. Similar to step 3, this re-acceleration checks for misfires, fuel trim, and the purge system under acceleration.
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Steady Speed – Part 2: Hold a steady speed between 55 to 60 mph (88-96 km/h) for five minutes. This extended steady speed segment is critical for the OBD2 system to monitor the catalytic converter efficiency. It also re-checks for misfires, EGR function, fuel trim, oxygen sensor performance, and purge functions.
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Final Deceleration and Stop: Decelerate (coast down) to a complete stop without using the brakes. This final coast-down allows the OBD2 system to perform a last check of the EGR system and the canister purge system as the vehicle comes to rest.
Important Considerations for Your 1999 Honda Accord:
- Safety First: Perform this drive cycle in a safe location where you can legally and safely perform these maneuvers. Avoid heavy traffic areas.
- Check Engine Light: If your “check engine light” is on, address those issues first. The drive cycle is designed to confirm systems are working correctly, not to fix underlying problems. Use an OBD2 scanner to read any diagnostic trouble codes (DTCs) and resolve them before attempting the drive cycle.
- Patience is Key: The drive cycle might need to be repeated more than once to set all monitors to “ready.” Don’t be discouraged if it doesn’t work on the first attempt.
- OBD2 Scanner: Consider using an OBD2 scanner to monitor the readiness status of your monitors before and after the drive cycle. This can save you time and confirm if the cycle has been successful. Many affordable scanners can display readiness monitor status.
- Specific Monitor Issues: If a particular monitor persistently refuses to set, even after multiple drive cycles, there might be an underlying issue with that specific system (e.g., oxygen sensor, EGR valve). In such cases, professional diagnosis and repair by a qualified mechanic are recommended.
By following these steps for the 1999 Honda Accord Obd2 drive cycle, you significantly increase your chances of getting your vehicle’s readiness monitors set and passing your next smog check. Remember to prioritize safety and address any pre-existing engine codes before starting the process. Good luck!
