Does the 'Check Engine Light' in your GM vehicle ever come on for no apparent reason? Why does this happen?

Question

Why do 'check/service engine lights come on for no apparent reason? And what issues might be going on with the vehicle or engine that are not easy to detect?

My 'check engine' light has gone off in the past because I left the gas cap loose. Even when rectifying this the light would stay on for a few days.

My light is on now but everything seems fine. It annoying.

Can it be turned off? Or do I have to wait for it to go off on its own? And what makes it go off on its own? Does the computer reset or something?

Answer 1

Read this for general information on how the OBD-II emissions system and check engine light is supposed to work:

http://www.samarins.com/diagnose/checkengine.html

http://www.troublecodes.net/articles/myth-conception.shtml

To see whether other owners of your car model complain of the same problem, register your car for free on http://www.mycarstats.com

OBD-II code readers that can turn the check engine light off until the fault occurs again are very inexpensive for anyone to purchase and use. The stored error codes in your computer can't be easily erased from memory. Once the problem has been corrected you have to complete a number of "drive cycles" sometimes to eventually clear the stored codes.

http://www.actron.com
Note that "code readers" simply readout and clear the active codes, but you need to buy a more expensive "scanner" to actually display the OBD-II data stream of diagnostic data flowing real time from the vehicle's computer.
http://www.actron.com/product_category.php?id=249

Answer 2

The OBD2 system detects some thing on two separate drive cycles that makes emissions higher and the light turns on. Gas cap or other that light stays on until the condition is fixed and is not seen by the engine controls for 30 to 50 ignition drive cycles. The light never turns on for no reason go to Auto - Zone write down the P0455 evap gross leak or other codes present and before they clear the code also write down the freeze frame data that tells mechanics what was happening when the code turned on the light. Then Auto-Zone will recommend what they think will fix your car and turn off the light. If the condition is not fixed the second time the computer sees the failure the CHECK ENGINE will be back. Locking gas cap's really set Lot's of lights.

Answer 3

This Site Might Help You.

RE:
Does the 'Check Engine Light' in your GM vehicle ever come on for no apparent reason? Why does this happen?
Why do 'check/service engine lights come on for no apparent reason? And what issues might be going on with the vehicle or engine that are not easy to detect?

My 'check engine' light has gone off in the past because I left the gas cap loose. Even when rectifying this the light would...

Answer 4

bobweb is correct.

The "Check Engine Light" on newer car models relates to how clean your powertrain is burning fuel.

The EGR (exhaust gas return) system is a likely candidate. An oxygen sensor failure is another.

Both of these are cheap. Go to your local auto parts dealer and get a free diagnosis. If it is your EGR, you are emitting excess pollution, but it won't hurt your engine. Your car has two oxygen sensors. The primary O2 sensor does effect your engine's performance and should be replaced. The secondary O2 sensor does not effect your engine's performance but is cheap and easy to replace. It is just a pollution sensor...if it is not working, your car is unable to detect the amount of oxygen (and unburned fuel) flowing out of the exhause pipe.

Answer 5

Autozone parts stores can check it for free and find out what codes are being stored on the computer---take it from there. If you unplug the computer fuse or the battery cables, it may take a while for the computer to reset itself and cause the car to run rough for a while---not the best way to do it. Best to find out what's setting off the light by the stored computer codes.
Batauto.com has info on trouble codes.

Answer 6

Even a slight thing like an open gas cap is not. It's not liquid gas that burns, but gasoline vapors. An open gas tank is an explosion waiting to happen (even set off by cellphone sparks). the check engine light is the worst idiot light ever, but it's there for a reason and should not be ignored. Have it checked at oil change; a simple computer reset might be all you need, or???

Answer 7

It's a strange thing. My friend has a 10 year old Toyoda pick up truck. Last weekend the check engine light came on. He just removed the battery and put it back in, the light went off and hasn't come back on.

Answer 8

i had the check engine light come on for a gas cap that was not closed properly. it went off after a few days. that is good but it also came on when my transmission failed. my car had only 174 miles on it so it was replaced under warranty. cars today are controlled by the on-board computer which is both good and bad.

Answer 9

YOU SHOULD GET THE VEHICLES COMPUTER SCANNED AND CHECK FOR ANY PROBLEMS AS WELL AS CODES AND THEN YOU WILL HAVE A GOOD IDEA ON WHAT THE PROBLEM TRULY IS.

TRY FINDING AN INDEPENDENT SHOP INSTEAD OF THE DEALER OR A CHAIN STORE BECAUSE YOU WILL BE OVERALL MORE PLEASED WITH THE FINDINGS AND THE SERVICE.

Answer 10

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If you recently filled up with gas and didnt put the gas cap on tightly that could cause it, but if not autozone will normally hook up an OBD scanner and read it for free.