Why is the "Check Engine" light sometimes on?

The "Check Engine" light is sometimes on my 2001 Toyota Corolla. We went to a lot of places to fix it but still it comes back.

Can someone help, i hope to fix it soon.

thanks

Update

My corolla is 2001 I had the codes run the other day. They said It is running lean and it also blows white smoke occasionally.. we have replaced the o2 sensor up front and number four coil as it suggested running better but still blowing smoke but mainly when first starting and when it warms up. what could be the problem? we also replaced leaking valve cover gasket. we have always kept oil in it.The car seems to run better since replacing #4 coil on plug. But we want to fix the lean mixture how is this done?

Answer this question I have this problem too

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I've got the same problem with my Corolla. I've taken it to a number of places and they say it's a fuel pressure issue. One mechanic recommended getting a new gas cap, which I did. No change. At this point I'm considering just breaking the light bulb because the light is so annoying.

by asdas

asdas, what error code did they give you?

by oldturkey03

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Go to Autozone or any other major automotive parts store & ask them for a free OBD (On Board Diagnostics) Code reader check. Hook it up to the car, pull the codes & let us know. Some times you may have to drive with scanner attached if it is a intermittent problem. There may be a lot of things to suspect.

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The check engine light can mean a variety of things. If it is not blinking it is typically related to the Emission Control Systems.

Take the car to an AutoZone, PepBoys, or any of the auto parts houses. They can plug the reader in and pull the code.

Typically it will mean;

- Gas Cap Loose

- O2 Sensors (Oxygen Sensor to determine how rich or lean the air fuel mixture is and whether the Catalytic Converter is doing it's job)

- MAS/MAF Sensor.

Anything can trigger it, it's best to have the code pulled and you can easily determine what the system is complaining about.

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tighten down your gas cap .check Eng. light is emissions."smog related"

watch and see if it comes on after fueling . about 10 min. down the rode .

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as regards fuel issue.

your fuel pump in the tank could be failing. never run the tank to the bottom. i've heatd of leakining injectors on these models. but right now i'm rebuiling a 2002 1.8 lit., corolla. cusomer just smoked it at 160,000. if the head was bad thats $390.00. if the engine core is unrebuildable than a used, 90 day garut., engine is no less than $1,100 , and then it's still a used engine. plkese rebuild your top -end at around 100,000 miles and rebalance. timing belts on time, and note to you mech. the tensioners fail prematurely,. go to 30,000 replase, not 60,000. and completely rotate out trans. fluid at 70,000 or more. some manufact. specs are wrong , torques wrong, factory quality contrl issues . go with your gut and still aplly old school rebuild ways.. we havn't had a rebuil return in 5 years.. Kraig

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My 2006 Diesel VW jetta occasionally has engine light problem. Took it to VW and received some suggestions from Wolfsburg to replace various wiring. Made my own determination that after a heavy rain, traversing puddles may cause engine light to turn on. When things dry out, light goes off.

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There is a very common problem with the Corolla that causes this.

It is a dirty MAF (MassAirflowSensor) and it can easily be cleaned.

There are several guides on the web, Google "Toyota corolla maf sensor". Expensive electronics cleaner is not needed, Isopropyl alchohol and a Q-tip will work fine.

You will need a scanner to reset the EngineCheckLight (Autozone or a friend) or I think it will automatically reset after about 40 times you start the car?

This is a 10minute repair. For some reason most professional mechanics do not know how to Google!

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Samy will be eternally grateful.

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