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Old 04-05-2011, 03:12 PM   #1
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Miles before check engine light reset

2 part question if anyone can help. I searched but couldn't find the answers.

#1) Can you actually "completely" reset the check engine light by disconnecting the battery? I disconnected the battery and the light went out but does that really reset the codes?

#2) Once the check engine light is reset, how many miles do you need to drive the car before it can pass inspection? I drove mine 109 miles and it did not pass the emissoins test?

Thanks for your help.
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Old 04-05-2011, 03:25 PM   #2
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To some degree, you are peeing into the wind here. Disconnecting the battery will clear most, but not necessarily all codes. While it will clear most emissions related codes, but if the problems are not repaired, the codes will re-trigger in a “pending” format waiting to see if the trouble persists.

Automatic clearing takes place if the code source is removed and does not return (e.g.: the car is repaired); but is dependent upon the number of cycles (cold start, full warm up, drive at speed, full cool down) more so than mileage.

This technology was instituted to prevent dumping the codes just before going to inspection; as you have found out, it works. Have the car scanned for codes, and fix the problem(s).
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Last edited by JFP in PA; 04-05-2011 at 03:31 PM.
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Old 04-05-2011, 03:48 PM   #3
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Thanks JFP, I should have mentioned that the check engine light was triggered by the faulty air oil separator that I replaced over the winter months. There is no question the separator was bad as it was blowing white smoke EVERY time I'd start the car.
Since the repair, I never had the light properly reset so I just disconnected the battery and it went away. Hence my question if that really reset it properly. Some cars it does...not sure about the Box.

My Volvo had the same problem and I was told that 80 miles would clear it out. I've done many start/stops...highway and city driving during the 109 miles. I though that would be enough to pass the inspection but it's not.
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Old 04-05-2011, 03:56 PM   #4
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+1 JFP - excellent reply.

Check for codes again and post them here...
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Old 04-05-2011, 03:57 PM   #5
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It is entirely possible that there is still another fault (or a third or fourth) that has yet to be identified and needs to be fixed as well. Get the car scanned, and then you will know what you are dealing with. You can buy a cheap scanner yourself for about $40-60 as well...............
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Old 04-05-2011, 04:13 PM   #6
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If any code still exists I will post it here.

But here's the question I really want to know.

Assuming there are no other repairs needed, and the light's been properly reset....how many miles do you need to drive the Boxster before it will pass an emmisions inspection?

Does anyone have experience with that?

Thanks
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Old 04-05-2011, 07:14 PM   #7
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Yes, I own a shop; we do this all the time. Once the car has been properly repaired, and the code(s) has been cleared, it should pass inspection immediately; no waiting or miles are required.
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Old 04-05-2011, 10:02 PM   #8
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Ummm,

After a battery disconnect or repair/code reset the car may need some miles to put the DME in "ready" state. I replaced my MAF a few years ago, reset the codes and went to get a smog cert. The operator said it was not in "ready" state and could not be tested until I had logged 30-50 miles. The same is true of a car that has been stored for winter with battery removed.

Relevant thread:
http://www.renntech.org/forums/index.php?/topic/19983-02-boxster-s-does-not-pass-emissions/
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Old 04-06-2011, 04:36 AM   #9
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You are correct, but what I a saying is that a shop can pass the car before the DME resets (I/M Readiness) under their discretion if they feel the problem for that specific code has been corrected. The DME still has to run the cycles before it totally resets to "Ready". But if you clear the codes by disconnecting the battery, the I/M Readiness test will show "not ready" for all the sensors the I/M test checks, and then no reputable shop will pass the car until the DME fully resets....
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