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why did my engine light go out today?
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trw
User
Mar 23, 2009, 4:42 PM
Post #1 of 6
(2056 views)
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why did my engine light go out today?
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I know this may sound weired but my 96 saturn 244,000kms
has had the check engine light on for the past
6 months back in november i used engine flush
and changed oil to synthetic and added BG MOA
additive to make the oil that much more better and
added a bottle of fuell stable in the tank.
and garaged it for winter with the ocassional start
up to keep the battery up to par. today i took it out
first time on the road and after driving 25 minutes
to my surprise it went out! why and what did i do
right? for the light to go out?  
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Loren Champlain Sr
Veteran
/ Moderator
Mar 23, 2009, 4:50 PM
Post #2 of 6
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Re: why did my engine light go out today?
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Bulb burned out? Turn the ignition on without starting the engine. See if the check engine light comes on. The PCM should store the trouble code that was there, regardless. And, you should check it. Ignoring it for 6 mos. is not the most idealistic thing to do.
Loren
SW Washington
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trw
User
Mar 23, 2009, 5:07 PM
Post #3 of 6
(2050 views)
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Re: why did my engine light go out today?
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Loren i did cycle the ignition key to on and the check
engine light does light up when starting the car and
goes out right after so in other words its doing its self
check and seeing nothing wrong and thats why it goes
out. 6 months prior to that i did get it scaned at saturn
dealer i was told i had a misfire on 2 cylinders and that
it was caused by carbon on the valves. or my teq said
it could be the valves not closing fully all the way down he also mentioned there was a poping sound coming out of
my exhaust thats why he said im giving you these conclusions based on what i hear and no about saturns
he also said that my engine was known for carbon build
up on valves 
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Loren Champlain Sr
Veteran
/ Moderator
Mar 23, 2009, 5:13 PM
Post #4 of 6
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Re: why did my engine light go out today?
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Good job! As far as carbon buildup, you can have a 'Motor Vac' injection cleaning done which will help that. Carbon buildup can cause pre-ignition which can actually melt pistons from excessive heat.
Loren
SW Washington
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trw
User
Mar 23, 2009, 5:31 PM
Post #5 of 6
(2043 views)
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Re: why did my engine light go out today?
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Good job! As far as carbon buildup, you can have a 'Motor Vac' injection cleaning done which will help that. Carbon buildup can cause pre-ignition which can actually melt pistons from excessive heat. THANKS!! for letting me no that and thanks for your asap posting Loren i will keep a close watch on the dash and keep you posted the next few days as to the engine light succes or not? P.S. Keeping my fingers crossed just maybe all that stuff i put in helped it.
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DanD
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Mar 26, 2009, 3:37 AM
Post #6 of 6
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Re: why did my engine light go out today?
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There are a number of different types of codes; I don’t just mean their # or what that # relates to. GM calls these codes; pending, current and history. Each code # has its own set criteria that the computer must see before the light is turned on (or off) to warn you of an issue and before the computer will act on an issue.
For example on some types of codes the computer must see an issue on three consecutive drive cycles before the check engine light will be turned on. A code will be set in the pending code library, at the first sign of an issue but no other action will be taken and the light stays off.
In this case of your misfire code, the computer constantly monitors for misfire and will flash the light or if the misfire is severe enough, turn the light on solid at the fist sign of a misfire issue.
Still talking misfire; the computer will also shut fuel down too that cylinder; in an attempt to protect the converter from overheating.
As you continue to drive the vehicle; the computer will randomly turn the fuel back on and see if the misfire is still there. If the engine continues to misfire; off goes the fuel again. But if for whatever reason the misfire is gone and after a predetermined time the computer will turn the light off. Some of these things happen in an instant; others take minutes, hours or even days.
The code that sets when the light was turned on; will be retained in the computers history memory for the next 60 drive cycles; after the computer turns the light off. If the condition isn’t seen during the 60 drive cycles; the code will be erased from the history memory.
The above is just scratching the surface of what happens with codes, warning lights and the computer(s) ability to manage the vehicle’s different systems.
Dan.
Canadian "EH"
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