Is My Car Ready for a Smog? Readiness monitors and Drive Cycle

Most 1996 and new vehicles have on board computers called an On Board Diagnostics II monitors (OBDII). OBDII contains information which is used to conduct smog tests, and determine smog test readiness. On average, there are 8-11 monitors that OBDII provides, and all these monitors must be in a ready state in order for a smog test to be completed. If you have changed your car battery, or disconnected power to your car, your readiness monitors can get reset. That means you need to drive your car in a variety of conditions in order to “exercise” the OBDII system and get the monitors in a ready state. If your car is not in a ready state, the smog check cannot be conducted.

Do All OBD2 Readiness monitors need to be “Ready”? 

The United States EPA has a slightly looser standards than California. For 1996-1999 cars, two monitors can be in a not ready state. For 2000 and newer cars, the United States EPA allows one monitor to be in a not ready state.

In California:

  • Gasoline Vehicles
    • 1996-1999 Gasoline Vehicles can have 1 monitor not-ready
    • 2000 and newer gas vehicles must have ALL monitors in a ready state with the exception of the EVAP monitor. 
  • Diesel Vehicles
    • 1996-2006 Diesel Vehicles can have 1 monitor in a not ready state. 
    • 2007 and newer Diese vehicles can have 2 OBD2 monitors in a not ready state 

How did my car get into a not ready state?

  • Battery disconnected or replaced. For example, if you have recently jump started your vehicle due to a weak battery, it’s possible the monitor information has been reset.
  • Vehicle computer updates or requiring an update
  • A problem either indicated by a check engine light, or soon to be reported by the check engine light
  • Clearing out the OBDII monitors using a scan tool.

Getting your OBD2 Monitors Ready – Performing a Drive Cycle

In order to get your vehicle in a ready state, you need to drive your vehicle in different conditions. This will naturally occur over time if you have not had any battery issue, or if there is no problem with your vehicle. But if you want to make sure, or you know you need to conduct a drive cycle, follow these instructions. Please note that depending on the model, make, and year of the vehicle, you will need to perform certain steps in order to get all the monitors in a ready state. You can follow the general instructions, or find your specific vehicle instructions below. 


Generic Vehicle Drive Cycle Instructions

Drive Cycle Instructions

Here are general instructions which should work for most vehicles. You should follow all traffic laws. You can perform this later at night so that there is less traffic. Don’t forget to be safe! 

  • Cold Start. Don’t leave your keys in prior to the cold start. (For example, after leaving the car overnight)
  • Idle for 3 minutes with electrical equipment on (A/C, headlights, and rear defroster turned on)
  • Turn off A/C and rear defroster.
  • Put the vehicle in gear, drive up to 35mph, and come to a complete stop. This should just be natural city driving for a few minutes.
  • Get on a freeway, accelerate smoothly to 55mph and maintain speeds for 3 minutes
  • Decelerate down to 20mph without braking or depressing clutch (for manual transmissions). Turn on hazard lights as needed.
  • accelerate smoothly to 55mph and maintain speeds for 5 minutes
  • Decelerate down to 20mph without braking or depressing clutch (for manual transmissions)

That’s it. You should be set to get to Antoich’s smog check now! 

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