How many drive cycles takes for engine light to go off after repair?

I am having new injectors put in to my 2000 Camry which we assume will solve all the misfire problems that caused the check engine light to go on. At this point since the obdii computer was zeroed, I’ve driven several hundred miles, so there’s a good chance I’ve completed a drive cycle.

So is my best bet to keep driving it a few days until the engine light goes off, at which point I go in for the emissions inspection OR do I zero it and then go through the drive cycles again? Which is likely to be sooner?


just checking for any responses --have to leave soon for repair shop. Any comments?


not sure for Toyota, but I believe Ford is 30 minutes of normal driving 3 times (hope this helps)

For misfire and fuel system monitors, if the fault does not occur on three consecutive drive cycles under similar conditions, the MIL is turned off.
Similar conditions means.

  1. Engine speed within 375 rpm compared to when the fault was detected.
    2.Engine load within 10% compared to when the fault was detected.
  2. Engine warm-up state or coolant temperature must match the temperature when the fault was detected.
    I believe you want to know how long till the light turns its self off. As you can see it is a little difficult to say exactly when your car will reset its monitor readiness status,one significant event sets you back to zero.
    I don’t think it looks good for you that several HUNDRED miles of driving (I conclude with on and off engine conditions)has passed and no light self reset,it seems someting is reoccuring and preventing a light self reset.

Reset the CEL now and see if you guessed right and it stays off…

Wanted to thank y’all for your answers. turns out the tech guessed right and zeroed it, so now–with all new injectors–at least one old one was proven bad–I should only have to drive one cycle (maybe 100 miles)to get those readiness monitors to check out, instead of 3 drive cycles to reset the engine light.

Let us know what you mean when you say “zeroed it”. Many mechanics say “cleared all codes” is this what you mean when you say zeroed it?

How did you come to the conclusion that one drive cycle with no reoccurance of the same fault will cause the MIL to reset?

Yes, by zeroing it I meant cleared all the does with the computer. As for drive cycles I wrote ‘3’ cycles to reset the engine light if it was not zeroed–based on what I heard here. and that was no guarantee either. I am hoping that with the codes cleared and the repair made, one drive cycle with no reoccurrance of the same fault will satisfy all the readiness monitors.

For a misfire, you may have to do some “hard” acceleration. I would have expected the light to go out with ten minutes of driving and accelerating twice. I don’t feel like reading the information again right now, but if the problem is fixed, the light should have gone out by now.

The specific misfire code may point right to the system that is causing the misfire. You might want to read your own codes with your own scan tool for around fifty dollars and get a Haynes manual to help with future codes because I expect that light to come right back on after three warmups and trips.

The check engine light should be turned off by whoever scans the DTC trouble code (and, records it). The car is, then, driven until the check engine light returns (or, not). The engine computer is scanned, again, and any DTC trouble codes recorded. Appropriate repairs are made, and the DTC trouble codes are erased. The car is driven, again, to see if the check engine light returns. If none does, the car is driven several “drive cycles” to allow the monitors to run their system sensor and actuator “health” checks. The monitors check just to insure that the sensors and actuators are ready to sense and to actuate.

Toyota has a 23 page TSB (Technical Service Bulletin), dated Feb. 8, 2002, “Readiness Monitor Drive Patterns”. It has lots of good stuff.

For around $100 you can get a code scanner that readiness monitoring. That is it will show you which systems have gone through enough drive cycles to be ready to be read. In New York State you can have one system not ready to read and still pass inspection as long as the check engine light is not on. On my car the evaporitive system is the last one to be ready,as much as 5 days driving. If you are going to buy a scanner be sure to get one with CAN ( the next standard after obdII ) on it.

Thanks hellokit for the Toyota Bulletin info–though it’s not specifically for a Camry should be helpful. Not always easy to execute those driving cycle routines in crowded traffic…

As for the scanner, I guess you’d get one that can read error codes PLUS the state of the readiness monitors. However I have found that in NY the law has been changed, recently I think–so that now you must have ALL the readiness monitors read. I argued this with a mechanic and the Toyota people since all the literature online says 2 systems for cars 96-2000 and one system for cars after that. But they insisted such readings will no longer be accepted by the NYS DMV when they upload their info to pass inspection for a particular car. I’ve heard that the EVAP and catalytic systems are the hardest to get ready. I think this is a bad change in the law, since the purpose of allowing a few systems to remain unready was an acknowledgement of potential computer error or misread. I think many motorists are suffering with this.

I had my car inspected in July2009 with ! system not reset. My mechanic told me it wouldn’t pass even though the check engine light wasn’t on. I told him to try it anyway and it passed.I think if there was a change in the law, that the first place it would show up would be on the New York State DMV website where this information is listed.

Thanks for the anecdote. I do notice that most of the bulletins on the NYS DMV site are a few years old. I want to make sure we’re talking about the same thing. (This is all new ground to me.) I was talking specifically about the readiness monitors–the applicable number of which in each car varies. Two sources said they now all have to show readiness and that the old allowances for one or two depending on the year no longer apply. There is also the matter of error codes and how many can register with the scanner and still not cause the engine light to go on. I believe that number is one or two. Perhaps your car passed because you had done sufficient drive cycle time to pass all the readiness monitors and despite your mechanic’s scanning of misfires or whatever they weren’t numerous enough to trip the engine light or fail the inspection.

what system will n.y.s. allow not to be readyto be read?i live hear too,and my inspector wont pass mine untill all can be read

well then your experience matches mine. the material online may be outdated. My mechanic says until last year or so some older cars could have two readiness monitors not pass, and one for cars from 2001 on. Now apparently you have to pass ALL of them in NYS. My advice is to get it diagnosed by the dealer --since that can sometimes be the hardest part. You can then have them repair it, or if you have a good mechanic that might be cheaper–dealers are usually more costly–get it done there.

Just want to tie up any loose ends on this thread. To recap, had my injectors repaired a week ago, codes were cleared. I drove around 130 miles in the interim, no engine light.Went to the testing station, no error codes, all readiness monitors passed except catalytic on their Mactools T-97 diagnostic tool. DMV passed it. So either that proves that at least one incomplete monitor is permitted or --as the other mechanic claims–that the T-97 falsely indicated the unready catalytic monitor meaning all monitors were actually ready. This seems possible given that we’re dealing with computers and diagnostic tools talking with each other. The only NYS DMV info online that I have found is:“The US EPA guidelines allow up to two monitors to be in a ‘not ready’ state for model year 1996 through 2000 vehicles, and one monitor ‘not ready’ for 2001 and newer model year vehicles.” (for vehicles subject to TLC or NYVIP OBDII inspection, the numbers are 3 and 2 respectively.) Same document (from 2004 I think)says that NYS has adopted the federal EPA guidance concerning readiness during OBD inspections. Have they changed recently? Can’t find evidence they have. Thanks for all the great answers.

Appears that you have “injested” some NY State emissions testing knowledge. Why don’t you stick around and help with people in similar circumstances?

thanks oldschool, well I’d feel a bit presumptuous given my overall lack of knowledge on cars, and I’m not sure I’ve solved it yet given the above scenario. But I will drop by on occasion and am always willing share my experience. I tend to find cars unbelievably complicated; I find HVAC much easier to comprehend ( given my amateur experience with it. Some of you guys on this thread have probably been taking your cars apart since high school or before.