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OBD 2 Drive Cycle Information

Lots of customers are having problems setting there monitors(drive cycles)                                                                                            You are not alone

OBD Drive cycles are required on 1996 and newer model vehicles.  Some vehicles are exempt.  Here is a link to the exempt vehicle list.  OBD drive cycle exemption list.

Hensley's Auto will test your monitors for you for free after you have completed a smog check with us, and have failed your smog check.  We do free re-test smog inspections unless otherwise stated.

OBD monitors are systems that the vehicle computer will check while driving.  An example of these systems would be EGR,CAT,AIS,EVAP,O2,HO2.  Different vehicles have different monitors.  Different vehicle manufacturers have different set criteria.

For Gas

1996-1999 model year only one monitor incomplete.  Doesn't matter with one.

2000 and newer vehicle only monitor that can me incomplete is evaperative.

One critical aspect of the Smog Check Program is the readiness of a vehicle's onboard diagnostic system (OBD II), which monitors the performance of emissions-related components. This article explains what a vehicle drive cycle is in the context of the Smog Check Program and how to set monitors to ensure your vehicle passes the inspection.

What is a Vehicle Drive Cycle?

A vehicle drive cycle is a specific sequence of driving conditions, including varying speeds, stops, and accelerations, designed to activate and complete the diagnostic tests of a vehicle's OBD II system. These cycles ensure that all emission-related monitors perform their self-tests and report their status accurately. If the monitors are not ready, the vehicle will not pass the Smog Check, even if it is otherwise running correctly.

Importance of Drive Cycles in the Smog Check Program

Drive cycles are essential for resetting and setting the readiness monitors. Readiness monitors are a series of tests performed by the vehicle's OBD II system to check the operation of emissions control systems. When a vehicle's battery is disconnected, or certain repairs are performed, these monitors are reset and must be completed again before a smog test.

How to Set Monitors for a Smog Check

  1. Pre-Drive Checks

    • Ensure your fuel tank is between 30% and 70% full.

    • Verify there are no pending diagnostic trouble codes (DTCs) using an OBD II scanner.

    • Ensure the vehicle is properly maintained and that all necessary repairs are completed.

  2. Starting the Drive Cycle

    • Begin with a cold start (the vehicle should be off for at least eight hours). Start the engine and let it idle for 2-3 minutes.

    • Drive at a steady speed of 20-30 mph for about three minutes. This helps warm up the engine and the oxygen sensors.

  3. Highway Driving

    • Accelerate smoothly to 55 mph and maintain this speed for at least 3-5 minutes. This allows the vehicle's catalytic converter to reach its operating temperature.

    • Avoid using cruise control to ensure natural speed variations.

  4. Deceleration

    • Allow the vehicle to decelerate naturally without using the brakes (coast down) from 55 mph to 20 mph. This process helps test the oxygen sensor and EGR (Exhaust Gas Recirculation) systems.

  5. City Driving

    • Drive at a steady speed of 25 mph for 2 minutes, then stop and idle for 3 minutes.

    • Repeat the stop-and-go driving to simulate typical city traffic conditions.

  6. Cooldown Period

    • Park the vehicle and let it sit for at least 30 minutes. This period allows the evaporative system monitor to run its tests.

  7. Recheck Monitors

    • After completing the drive cycle, use an OBD II scanner to check if all monitors are set. The critical monitors for the Smog Check include the catalytic converter, oxygen sensors, EGR system, and evaporative system.

Tips for Successful Monitor Setting

  • Consistency: Drive the vehicle consistently during the cycle. Sudden stops, hard accelerations, or varying speeds can interrupt the monitor setting process.

  • Multiple Attempts: It may take several attempts to complete all the monitors, especially if the vehicle's battery was recently disconnected.

  • Professional Help: If you're having trouble setting the monitors, consider seeking help from Hensley's Auto.  If you have driven your vehicle over 500 miles we can run a diagnostic to see why the moniitors are not setting.


Setting the monitors through a proper drive cycle is crucial for passing California's Smog Check Program. By following the outlined steps and ensuring all readiness monitors are complete, you can avoid the inconvenience of a failed smog test. Regular vehicle maintenance and adherence to the drive cycle procedures will help keep your vehicle in compliance with emissions standards and contribute to a cleaner environment.

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