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Registered User
Join Date: Feb 2005
Location: Costa Mesa, CA
Posts: 142
Porsche Crest 993 Drive cycle

Does any one have a entire and detailed list of the requirements to complete the drive cycle so the car can be legally smogged in southern California?
Old 12-06-2016, 06:03 PM
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Registered User
Join Date: Oct 2009
Posts: 345
From a post on Rennlist by B-Line:

If your battery has been disconnected, you are most certainly going to have to reset all your OBDII flags for smog check.

Your car might be running perfectly but if you don't reset your OBDII flags with this archaic procedure, you will repeatedly fail.

Over the past 15 years of owning my 993, I have had to execute the Porsche drive cycle approximately every other year to prepare my vehicle for smog check in California. I have had varying success and failure and decided to make an even more comprehensive direction list to follow.

Referee stations no longer allow you to get a sign off. Driving the car a few hundred miles does not work.

I most recently failed to clear my flags after 4 late-evening attempts and then got it to work on the 5th attempt. When the flags did clear, I was gently reminded of what has and has not worked over the past decade and a half.

1) Get an OBDII reader that you plug into your OBDII port by the drivers side right knee. I recommend:
This reader will tell you when your flags have been reset and you are ready to go for smog check.

2) Do the drive late at night so you can flow it as interrupted as possible. Have a timer handy so you know you have met your triggers. It is okay if the drive cycle is interrupted during the procedure... It's cumulative. as long as you
- Turn off the car
- Exceed 60 MPH
- Exceed 3000 RPM

3) The drive cycle is as follows:
- Start the car and idle for 2min10sec
- Drive the car between 20mph and 30mph for 3min15sec
- Drive the car between 40mph and 60mph for 15min
- Come to stop and idle in neutral for 5min

4) Do not go into Reverse. Prepare the car the day/night before by making sure you do not need to go into reverse. Back into the garage or park in the driveway so you can drive straight out. Reverse may cancel the drive cycle.

5) Do not use cruise control. I believe this is the repeated mistake that I make every other year.

6) Do the drive cycle when the car is cold. If you have driven the car in 4 hours before you attempt the drive cycle, it will not work.

7) When you plug in the OBDII, you will likely have 3 solid circles and about 7 that blink. The yellow ? light will be illuminated and the OBDII reader will beep about every 30 seconds. The blinking flags will ALL reset at the same time. They DO NOT reset one at a time. It's all or nothing. And when they do reset, the OBDII green light with the check mark illuminates.

8) Even if you do everything perfect, it is likely it can take 2x to do this process. Don't bother trying to do it back to back. It won't work. Go home, park the car and try it again the next night. (Don't forget to park the car so you don't have to reverse the next night.) - You might get lucky and it will clear the flags the first time you do it... But don't count on it.

Once you get the green light.. You are good to smog.

So remember:
1) Car should be cold
2) No not go into reverse
3) Do not use cruise control
4) Do not exceed 60 mph
5) Do not exceed 3000 RPM
6) All flags go from blinking to solid at the same time when cycle is complete and the OBDII reader goes from yellow to green light
7) It is okay to stop and go (traffic lights, etc.) the drive cycle is cumulative.
8) It will likely take 2x of doing the drive cycle to clear the flags

That's 15 years of research.... Print this out, store it in your car with an OBDII reader. You will forget in two years what the detailed instructions are. You will find other posts that don't have ALL the information and you will make many of the mistakes I made.
And pass the OBDII and instructions to the new buyer should you ever sell the car.
Old 12-06-2016, 06:16 PM
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Location: Costa Mesa, CA
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Great Terry. I will give it a try. It sounds like I should have someone in the passenger seat with a stopwatch.
Old 12-07-2016, 12:30 PM
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Join Date: Aug 2009
Location: San Diego, CA
Posts: 297
Drive Cycle

Its a pain in the rear to do it and get it right. I think it took me three tries. Then I had some work done on the car again and they said I'd have to do it again. Yippie?
1956 Speedster
1959 A Coupe
1966 911R (under construction)
1986 GT3 CC16
1998 C2S
Old 12-29-2016, 03:29 PM
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