Scan tool question

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  #1  
Old 08-21-15, 01:43 PM
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Scan tool question

Made repair to vehicle. Cleared check engine light when battery disconnected. I understand my vehicle now needs to run thru its diagnostic cycle before passing an emission testing. I stopped at the parts store and they put their scantool on it and it found no codes.

So my questions:

1. Does the vehicle have to complete that diagnostic cycle before it would throw other codes unrelated to the clearing? Or in other words, if my repair was not successful, would I have to wait for it to confirm the diagnostic cycle before getting another code related to that?

2. Since no codes were found with the parts store scan tool, does that mean the vehicle has completed its diagnostic and now has a clean bill of health?

Thanks
 
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  #2  
Old 08-21-15, 02:07 PM
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Sometimes you have to drive a couple hundred miles to get the system to reset itself.
 
  #3  
Old 08-21-15, 02:37 PM
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No codes were found because they were erased when the battery was disconnected. As mentioned, it will take several hundred miles to be ready for a smog test. If any codes are detected during that time, they will be recorded as they happen. An infrequent code may not recur for many miles, until the condition that caused it repeats itself.
 
  #4  
Old 08-21-15, 03:00 PM
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So your sure the diagnostic doesn't have to complete for the vehicle to give codes like it normally would?

I assumed nothing would be shown until I complete the mileage/diagnostic checklist.
 
  #5  
Old 08-21-15, 03:09 PM
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No it does not need to complete the cycle before it records new codes. And no, I don't think you can assume that a past code is fixed, based on starting the car and only driving it a few miles. Probably depends what code was thrown. Some codes are temporarily stored and do not become a permanent code until certain criteria are met. Just depends.
 
  #6  
Old 08-21-15, 04:00 PM
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Does the scantool tell you if you have passed the "readiness" bullcrap? No codes = ready?
 
  #7  
Old 08-21-15, 04:24 PM
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It should, mine does.

And no, no codes does not = ready. As mentioned, the car must complete its diagostic of all emissions systems which can take a while.... multiple driving cycles... perhaps 100 miles or more.
 
  #8  
Old 08-21-15, 04:47 PM
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It was found that drivers were clearing codes right in front of the inspection stations and in line so they built a drive timer into the computer. It could be as little as 5 miles or as much as 50 miles.

Inspection will not fault you if the system is in a "not ready state" but you will get a red sticker and have to go back.
 

Last edited by PJmax; 08-21-15 at 08:22 PM. Reason: typo
  #9  
Old 08-21-15, 06:51 PM
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1. do not clear codes. FIX PROBLEM. You are masking issue and it will come back at you. Maybe with vengeance.
2. what is the vehicle in question? Never heard of driving cycle to be hundreds of miles. Example here (and how long does this take? 30 minutes or so?)

General Motors Driving Cycle
 
  #10  
Old 08-22-15, 06:32 AM
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Easy, Igor.

"Made repair to vehicle".

 
  #11  
Old 08-22-15, 06:49 AM
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Sure. Don't mind apologizing at all.
And this means what? before it would throw other codes unrelated to the clearing?
 
  #12  
Old 08-22-15, 07:19 AM
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My ford takes at least 300 miles... I think the EVAP is the last one to clear the check.
 
  #13  
Old 08-23-15, 02:00 PM
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I won't even waste time on this post as I have no idea about the make/year/model of the vehicle nor what repair was performed.

My crystal ball is broken.
 
  #14  
Old 08-24-15, 07:31 AM
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One of the data items available to be read by better scan tools is "miles since reset"--so yes they CAN tell if you recently cleared the codes. The question is whether they care, or have any training. Therefore, YMMV.
 
  #15  
Old 08-24-15, 09:54 AM
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Found this to be a useful article discussing the difference between pending, current, and permanent OBD codes and the Universal Drive Trip Pattern that must occur before the car is "ready" for smog testing. Taking A First Look At Permanent DTCs - CARS Magazine
 
  #16  
Old 08-25-15, 03:48 PM
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Thank goodness I don't have to deal with emissions with the way I register cars, nonresident plates from a different state are so much easier
 
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