The OBD-II drive cycle is a series of driving maneuvers required to set readiness monitors for emissions testing. Completing this cycle is crucial for passing a smog check if your Honda Accord’s check engine light is on or if the OBD-II system isn’t ready. Here’s a breakdown of the general OBD-II drive cycle, often applicable to a Honda Accord, but always consult your owner’s manual for specific instructions.
Understanding the OBDII Drive Cycle
The OBD-II drive cycle starts with a cold start. This means the engine coolant temperature must be below 122°F (50°C) and the difference between the coolant and air temperature sensor readings should be less than 11°F (6°C). Importantly, avoid turning the ignition key on before the cold start; doing so might prevent the heated oxygen sensor diagnostic from running.
OBDII Drive Cycle Steps
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Idle Phase: After starting the engine, let it idle in Drive for two and a half minutes with the air conditioning (A/C) and rear window defroster turned on. This phase allows the OBD-II system to check the oxygen sensor heater circuits, air pump, and evaporative emission (EVAP) purge system.
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Acceleration and Cruise Phase 1: Turn off the A/C and rear defroster. Accelerate to 55 mph (88 km/h) at half throttle. This tests ignition misfire, fuel trim, and canister purge functionality. Maintain a constant speed of 55 mph for three minutes. During this steady state, the OBD-II system monitors the exhaust gas recirculation (EGR) system, air pump, oxygen sensors, and canister purge.
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Deceleration Phase 1: Decelerate to 20 mph (32 km/h) without using the brakes or depressing the clutch. This allows the system to check EGR and purge functions during deceleration.
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Acceleration and Cruise Phase 2: Accelerate back to 55-60 mph (88-96 km/h) using half throttle. This repeats the misfire, fuel trim, and purge checks.
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Cruise Phase 2: Maintain a steady speed of 55-60 mph for five minutes. This extended period allows the OBD-II system to monitor catalytic converter efficiency, misfire, EGR, fuel trim, oxygen sensors, and purge functions thoroughly. This phase is crucial for evaluating the catalytic converter’s performance.
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Deceleration Phase 2: Coast down to a complete stop without applying the brakes. This final deceleration allows for a final check of the EGR system and canister purge.
Completing the Drive Cycle
Successfully completing the OBD-II drive cycle may require multiple attempts. Interruptions or deviations from the specified parameters can reset the process. Once completed, the readiness monitors should be set, allowing your Honda Accord to pass emissions testing. If problems persist, consult a qualified mechanic to diagnose any underlying issues. Remember to check your specific Honda Accord model’s owner’s manual for detailed drive cycle instructions. Variations may exist depending on the year and engine type.
