How to Do BMW OBDII Drive Cycle for Smog Check




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Why do I need to do a drive cycle?
If you have recently changed the battery on your BMW or done a major repair for the engine or emission system, the on board computer has mostly been reset. This makes the car not ready for a smog check. In order for your car to pass the smog check, you need to do a drive cycle to get the OBC ready.

This process can be either cost consuming or time consuming. You could either drive a whole 200 miles hopefully the OBC is ready or do as BMW dealership had suggested to drive 30 miles, park the car in idle for 30 minutes, and repeat this process for at least 3-4 times. Both of these methods are extremely time consuming but there is another way to get the OBC ready to pass the smog check.

OBD-II Driving Cycle:
If you have a 1996-up BMW, you have the OBD-II diagnostic system that constantly monitors the sensors and solenoids on the engine. You will need to do a Driving Cycle if you have replaced the battery, disconnected the battery, or cleared the codes after a repair. The Driving Cycle performs a diagnostic test on all the systems that the computer monitors. Fortunately, this cycle can be completed in at least 15 minutes if done correctly.


  • Do this at night, around 10pm-12am when there's less traffic (also police) on the road

  • Choose a freeway that's generally empty around this time and drive on the
    most right lane

  • Bring all necessary documents in case you are pulled over by the police

  • Make sure the car has a full tank of gas

  • Allow the car to cool down for at least 3 hours so the engine bay
    temperature is less than 50°C/122°F

  • If you are doing this in the winter, wear extra layers - you cannot turn on
    the AC

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Step 1: Cold Start

The engine coolant temperature must be below 50°C/122°F and above 6°C/11°F of the ambient air temperature during startup.

Don't leave the key on before the cold start or there is a possibility that the heated oxygen sensor may not run.

Step 2: Idle

Run the engine for 2.5 minutes with the rear defroster on and the AC on maximum. The more electrical load, the better.

This tests the Passive Air, O2 heater, Purge "No Flow", and Misfire. If you can achieve a closed loop, then the Fuel Trim will also be tested.

Step 3: Accelerate

Turn off air conditioner, radio, and other loads. Apply a half throttle until you reach 55mph. Make sure to drive on the right most lane.

This tests the Misfire, Fuel Trim, and Purge Flow.

Step 4: Maintain Steady Speed

You must maintain a steady speed of 55mph for 3 minutes.

This tests the Air Intrusive, Misfire, EGT, Purge, O2 Response, and Fuel Trim.

Step 5: Decelerate

Release your foot from the accelerator pedal. You must not shift or touch the brake/clutch. The vehicle must gradually coast down to 20mph. Now is a good idea to turn on your hazard warning lights to let other cars behind you be alert on what's going on. They may even high beam you in the process. This is why you need to already be in the most right lane.

This tests the Purge, EGR, and Fuel Trim.

Step 6: Accelerate Again

Accelerate at 3/4 throttle until you reach 55mph again.

This tests the Misfire, Fuel Trim, and Purge Flow again.

Step 7: Maintain Steady Speed Again

You will now maintain a steady speed of 55mph for 5 minutes.

This performs additional diagnostics as well as the catalyst monitor. However, if the battery has been disconnected or the catalyst is marginal, it might take you 5 entire driving cycles to complete.

Step 8: Decelerate

Once again, don't brake, shift gears, or press the clutch.

This performs the same tests as step 5.

Step 9: Good Luck

If at any time you have to speed up, change lanes, or break steps 3-8, you must start the driving over. If the process goes well, you will only have to attempt this once, but it shouldn't take more than a few times to complete the Driving Cycle. Good luck!

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    11 Discussions


    3 months ago

    Thank you so much for the great instructions! I planned it around one of my tour routes and made it! CaliFunDay - #CaliFunDay Tours & Transportation...


    Question 6 months ago on Introduction

    If I only need to get the catalyst and o2 sensor ready (incomplete) do I still need to follow every step?


    Question 1 year ago on Step 2

    I am leaving from my home I do not live on the highway so is there a break in between Step 2 and step 3 because I can't accelerate 2:55 until I get to the highway which would be about 5 extra minutes will this break the cycle

    1 answer

    Answer 1 year ago

    After the 2:30 min idle, I just drove about 3 miles to the highway and stayed under 55mph and not exceed 2500rpm. Once on highway, I began the rest of the progress. After doing the cycle about 3 times just to be safe. I came to a complete stop in gear and stalled. Went to smog next day and passed!


    2 years ago

    I know this post is a little bit old but I have to do this test because i recently installed a new battery on my 04 x5 3.01 and failed my inspection test twice because odbii not ready. i live in bk nyc where every 100yrd is a stop sign and traffic light also the closest hwy is about 6 miles from me. after step 2 can i drive the car normal until i reach highway to start this test or will i have to speed up to 55mph after performing step 2. reason im asking because i heard you're not supposed to used brakes or past over 60mph or more than 3000rpm

    2 replies

    Reply 1 year ago

    Did you ever get an answer to your question? I am in the same predicament and trying to figure out how to get from Step 2 to step 3 without breaking the cycle but I see no new information on this question or any of the questions answer


    Reply 1 year ago

    jnard10 did you get a reply


    3 years ago

    Can you perform this on a dyno or on jackstands with the wheels in the air? or perhaps without wheels with the car on jackstands? That way you won't be on the road (with an expired tag?) and you can do this from the comfort of your hopefully well ventilated garage or even backyard. I've read the test will be nullified if you exceed 60mph, give large fluctuations in throttle, or go over 3000 RPM. To make things easier, I use cruise control, but I'm not sure if that invalidates the test either...

    1 reply

    Reply 1 year ago

    I have the same questions as the last 4 comments can we get an answer


    3 years ago

    Good questions dcurrie2! I was thinking the samething. Can I leave my scanner hooked up while performing the drive cycle to see if everything are good to go?