How to do the OBDII drive cycle?

Status
Not open for further replies.
Joined
May 30, 2008
Messages
2,376
Location
New York
I recently changed out a couple of O2 sensors and in order to get the monitors to ready I understand there are two options: drive for some amount of time and eventually you get the readies, or go through the special OBDII drive cycle. However, I can't for the life of me figure out how I could do the drive cycle. Sure, I could start from cold and run a few minutes, but then accelerating up to 55 for three minutes and then coasting down to 0 and back up again and all the rest would be impossible from my house or on any roads I can think of around here where I could possibly park my car long enough to cool off. Virtually every spot I can think of would require multiple starts and stops, or up and down speeds to get to 55 mph and then holding for three minutes might not be possible. How do you folks do it short of parking at your local race track over night?
 
Sunday morning?

I presume

1) you need to pass a smog inspection real soon and
2) there are other monitors, like EGR, that have to wait for the 02 sensor to run before they run.

My state allows 2-3 I/M monitors incomplete as long as there's no CEL at inpection time. However, if something early in the chain is incomplete, it holds up the rest of the line.

Speaking from GM generalities, half the monitors run PDQ, as in before you warm up fully from the first cold start, or even leave your driveway. The EGR one has been a toughie for me on my 97 Silhouette 3.4 but I finally got it to run on a coastdown from 50-20 MPH. I manually downshifted the automatic transmission to make this coastdown happen faster... and I had a scantool with me plugged in that blinked from NR to Ready in real time.
wink.gif
 
What year vehicle? 1999 or earlier lets 2 emissions monitors go untested. 2000+ lets 1 go undone.

Just drive it normally for a week. Then go get it tested. Nobody "should" notice an inspection that's a week overdue. Except a hawk-eyed meter person, who can give you a ticket for that...
 
That's why a sniffer up the tail-pipe would be better than the mickey-mouse system they are using IMO.
21.gif


Who cares what is/isn't working when what comes out of the tailpipe is what really matters!
thumbsup2.gif
 
It varies by manufacturer. In general, it's something like this (which I found in 3 seconds by Googling, by the way):


NOTE: The ignition key must not be on prior to the cold start otherwise the heated oxygen sensor diagnostic may not run.

1. As soon as the engine starts, idle the engine in drive for two and a half minutes with the A/C and rear defrost on. OBDII checks oxygen sensor heater circuits, air pump and EVAP purge.

2. Turn the A/C and rear defrost off, and accelerate to 55 mph at half throttle. OBDII checks for ignition misfire, fuel trim and canister purge.

3. Hold at a steady state speed of 55 mph for three minutes.

OBDII monitors EGR, air pump, O2 sensors and canister purge.

4. Decelerate (coast down) to 20 mph without braking or depressing the clutch. OBDII checks EGR and purge functions.

5. Accelerate back to 55 to 60 mph at half throttle. OBDII checks misfire, fuel trim and purge again.

6. Hold at a steady speed of 55 to 60 mph for five minutes.

OBDII monitors catalytic converter efficiency, misfire, EGR, fuel trim, oxygen sensors and purge functions.

7. Decelerate (coast down) to a stop without braking. OBDII makes a final check of EGR and canister purge.
 
D---, I'd hate to try to accomplish that sequence even out in the middle of Nowhere, Montana. Sounds like a good way to get one's self run over just about anywhere, let alone in New York!
 
LOL...seriously, go drive around town for 30 minutes and you'll probably do all of those things.
 
In general, I've found that about 8 miles of 25-35MPH driving followed by about 8 miles of 55MPH driving gets all of the monitors completed.
 
It's a 2003 Chevy Impala with the 3.4 engine, about 68,500 miles. Here's the sequence of events. 1) Got a check engine light and checked codes which indicated one bad O2 sensor and one going out. 2) Replaced both, but in the process I disconnected the battery to avoid shocks/sparks. 3) Cleared codes and drove around normally for a couple of days. No lights and no codes, but I forgot to check readiness. 4) Took in for inspection and it failed because of two non-ready monitors: catalyst and evap system. 5) Got a 10-day extension on the inspection. I've been driving the car around normally for another couple of days and the catalyst now shows ready, but not the evap monitor. I'll have to look up whether or not having one monitor not ready would allow me to pass inspection. I thought of trying that OBDII drive cycle listed above by dparm in order to reset the monitors to ready, but I can't dream up anyway of doing it. It's almost as if they came up with a cycle that would be impossible for ordinary people to do, forcing you to take it into a shop.
 
GMs need the gas tank between 1/4 and 3/4 to run the charcoal canister monitor.
 
Just speaking from experience, it is a pain to complete a drive cycle in any reasonable amount of time. I dealt with OBDII vehicles for 6 years and it was always a pain (FoMoCo). I had my test route all set up (10 miles), check sheet, and a DCL capable scanner to keep an eye on things, and it was still a 50/50 proposition as to whether the cat monitors would complete their test. It almost like it completed the drive cycle faster when you completely ignored everything and just drove it.
 
Ford vehicles have two different cat monitors.

One of them likes to complete at 55MPH steady-state driving.

The other likes to complete during 25-35MPH steady-state driving (and in fact does so much quicker than if you drive it faster).

The type of driving required to get the cat monitor to complete is very different between these two types.
 
I believe in NY 2003 model should pass with one incomplete as long as it is NOT catalytic converter. You should be able to pass the inspection. You can always ask the guy before getting it hooked up to make sure.

- Vikas
 
Normal and varied driving is best. Varied speeds, starts, AC on/off, idling, etc.
The convoluted sequence by some mfrs is absurd, and has not worked in some cases - a total waste of frustrating time.

But you need a bunch of starts, for sure. They don't want to see a freshly cleared computer roll in the the emissions test area!
 
Status
Not open for further replies.
Back
Top