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How long can it take for engine sensors to gather enough data?

 
 
DrewDad
 
Reply Sat 18 Apr, 2009 04:27 pm
I had work done on my car (2001 Toyota Corolla) over a week ago. (They did the work to fix the check engine light. Mass airflow sensor and engine idle airflow solenoid, or somesuch.)

I've driven over 200 miles. The state inspection place tells me that two of my sensors are still reporting "not ready", which means I can't get my sticker....

Is it just mileage driven? Or can it be other things as well, like the number of times the engine is started?
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Type: Question • Score: 4 • Views: 24,177 • Replies: 23
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littlek
 
  1  
Reply Sat 18 Apr, 2009 04:44 pm
My understanding of the process is this: The computer that assesses the check engine light just tells the mechanics what system is faulty. It may be more targeted than that, but at least sometimes isn't much more tuned. So, there's a little artistry in interpretation by the mechanic. My car was stalling in humid/rainy weather. One shop ran the diagnostic and checked the distributor and found it was wet inside (BIG puddle). He dried it out, but in humid weather the car was still stalling. I brought it to another garage and that guy got the same message from the diagnostic machine, but found that the wires to my spark plugs were also exposed to the humid air. Once he fixed that, all was fine.

Not sure all that answers your question.
0 Replies
 
hawkeye10
 
  1  
Reply Sat 18 Apr, 2009 05:19 pm
when I had emission sensor problems 6 months ago my mechanic told me that the longest it takes for the computer to reset to current conditions is the next start.
Chumly
 
  1  
Reply Sat 18 Apr, 2009 05:21 pm
@DrewDad,
It's not just mileage driven, it's also throttle position etc. To make sure the ECU is up to speed (pun) run your vehicle at all throttle and gear settings (well all the throttle / gear settings you can practically manage).

That being said, 200 miles should be more than enough to cover the needed conditions, however it will no harm to run through all the throttle / gear settings you can practically manage.
DrewDad
 
  1  
Reply Sat 18 Apr, 2009 10:29 pm
@hawkeye10,
hawkeye10 wrote:

when I had emission sensor problems 6 months ago my mechanic told me that the longest it takes for the computer to reset to current conditions is the next start.

That contradicts what my mechanic and the state inspection guy told me.

Now, the check engine light came back on after replacing the first sensor, so the computer was able to immediately determine that there was a problem. But the sensors have to gather enough data before the car can pass inspection.
0 Replies
 
DrewDad
 
  1  
Reply Sat 18 Apr, 2009 10:30 pm
@Chumly,
So maybe 60 miles of city driving will take care of it, but 200 miles of highway cruising will not?
Rockhead
 
  1  
Reply Sat 18 Apr, 2009 10:42 pm
@DrewDad,
I'm just getting my feet wet with OBD2 again, but my experience is several cool down and run periods at least to gather enough info.

I have been chasing a bug in a 2001 Durango, and it takes a couple days to reset the code.
Chumly
 
  1  
Reply Sat 18 Apr, 2009 11:19 pm
@DrewDad,
Firstly Rock is wrong as to "several cool down and run periods" per se.

The data needed to confirm full status is not solely dependent on "several cool down and run periods" as discussed it must include certain throttle settings, engine load etc. The ECU needs all operations for given parameters, again some of which I've discussed and advised you as to how to facilitate.

Also your mech is a dork because he should know it's possible to avoid all this hassle and "tell" the ECU in advance that all parameters have registered. Dealers are cool in this regard!

Understand also that I said "200 miles should be more than enough to cover the needed conditions, however it will do no harm to run through all the throttle / gear settings you can practically manage."

Understand also that it's not mileage per se, it's the requisite variances as sent from the sensors that the ECU needs.

Having said all that, if I was to guess as to the source of the problems, and if the ECU, and wiring, and fuel delivery, and catalytic converter, and ignition system etc are all fine - and you run through all settings as I've advised - then some sensors have either not been installed correctly or have failed.
DrewDad
 
  1  
Reply Sun 19 Apr, 2009 09:43 am
@Chumly,
Wouldn't the computer mark the sensors as failed, then?
DrewDad
 
  1  
Reply Sun 19 Apr, 2009 09:43 am
@Rockhead,
Rockhead wrote:

I'm just getting my feet wet with OBD2 again, but my experience is several cool down and run periods at least to gather enough info.

I have been chasing a bug in a 2001 Durango, and it takes a couple days to reset the code.

Well, it's had that. I'm just trying to figure out what I need to do to get the damn thing to pass inspection....
0 Replies
 
Chumly
 
  1  
Reply Sun 19 Apr, 2009 09:53 am
@DrewDad,
That depends what you mean by "failed" (too vague) because until all required parameters have been sent by establishing all running conditions, things won't be normalized. Error codes prior to normalization are not overly meaningful.

Run the vehicle as I've suggested (or get someone who knows what they're doing to set the ECU) and then report the remaining specific codes (if any).

I have a laptop-based OBD2 reader that can do real-time data-logging, that's a cool way to approach these problems.
Walter Hinteler
 
  1  
Reply Sun 19 Apr, 2009 10:00 am
@DrewDad,
The mechanics just reset my car's computer and all is on "okay" again.
(My temperatre sensor was fitted two weeks ago: the computer got the correct data within seconds after the engine started.)
Chumly
 
  1  
Reply Sun 19 Apr, 2009 10:12 am
@Walter Hinteler,
There are different definitions of the word "reset" as it relates to the ECU!

One definition is removing the power (or resetting) the ECU long enough for it to go back to its default settings. After which it must regather all parameters before the CEL will extinguish.

Another definition is sending the ECU data that all parameters are OK, this is typically done by mechs at a dealer. After which the ECU need not regather all parameters and the CEL will not light up (unless there is a recurring problem).
0 Replies
 
Chumly
 
  1  
Reply Sun 19 Apr, 2009 10:34 am
Here is the unit I use

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Rockhead
 
  1  
Reply Sun 19 Apr, 2009 11:07 am
@Chumly,
cost?
Chumly
 
  1  
Reply Sun 19 Apr, 2009 11:56 am
@Rockhead,
There are cheaper gizmos but real time data logging can be very helpful.

US $194.95

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DrewDad
 
  1  
Reply Sun 19 Apr, 2009 01:44 pm
@Chumly,
Chumly wrote:

That depends what you mean by "failed" (too vague) because until all required parameters have been sent by establishing all running conditions, things won't be normalized. Error codes prior to normalization are not overly meaningful.

The computer reports two sensors as "not ready". There are no error codes. In Texas, if two or more sensor report "not ready", then the car does not pass inspection.
Chumly
 
  1  
Reply Sun 19 Apr, 2009 02:10 pm
@DrewDad,
Well unless you have a decent OBDII reader you cannot know if there are stored codes or not. Understand that the dashboard CEL is not a tell-all indicator by any means.

Here in BC we have "AirCare " and thus a strict ritual of OBDII educated inspectors reading both stored and active codes.

I don't know exactly what you mean by: "The computer reports two sensors as not ready" however I assume this is something your mech told you but I have no way of knowing exactly how he obtained that information, nor how accurate it is in this specific context, nor what reader(s) he used, nor how educated your mech is in OBDII diagnostics etc.

Again.........having said all that, if I was to guess as to the source of the problems, and if the ECU, and wiring, and fuel delivery, and catalytic converter, and ignition system etc are all fine - and you run through all settings as I've advised - then some sensors have either not been installed correctly or have failed.
0 Replies
 
Rockhead
 
  1  
Reply Sun 19 Apr, 2009 02:13 pm
@Chumly,
that's about what the one I am looking at buying costs, but it does not require a laptop.

(my laptop is more trouble than its worth anymore...)
Chumly
 
  1  
Reply Sun 19 Apr, 2009 02:31 pm
@Rockhead,
Then you have to decide if the one your thinking of buying can perform all the tasks you want it to as compared to the Dyno-Scan for Windows.
0 Replies
 
 

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