What causes the 'check engine' light, in general?

[beer]

Last May was the first time I had seen the 'check engine' light in my ford 98 Contour. I noticed a decrease in power and an increase in gas milage - my O2 sensor had gone out, I thought. I had a diagnostic run, and that was indeed the case. I had it replaced and taken care of - the light never came back on again.

I was driving down IH-35 last week and the light came on again. I had been carefully watching my engine powerband and gas milage, and didn't notice and real change. However, I know that the check engine indicator is tied to emissions components more than anything. Today, the light went off, and hasnt' come back since. What could have been causing it?

 

[AgaBoogaBoo]

Q. What causes the 'check engine' light, in general?
A. The engine

 

[beer]

Originally posted by: AgaBooga
Q. What causes the 'check engine' light, in general?
A. The engine

worthless

 

[conjur]

Error codes thrown by some component of your drivetrain.

Take it Autozone and have them check the error codes for free.

 

[LAUST]

emissions

can be anything from a faulty O2 sensor to your gas cap not being on tight enough

 

[beer]

Originally posted by: LAUST
emissions

can be anything from a faulty O2 sensor to your gas cap not being on tight enough

In most cases, will it cause me to fail emissions tests? (non-CA)

 

[Evadman]

Originally posted by: Elemental007

Originally posted by: LAUST
emissions

can be anything from a faulty O2 sensor to your gas cap not being on tight enough

In most cases, will it cause me to fail emissions tests? (non-CA)

Depends on how they check emissions. in IL you instantly fail if your check engine light is on.

 

[Ronstang]

Sometimes the feedback from sensors is out of range and trips the "check engine lihgt" yet goes back into range and eventually turns the light back off. These can be due to anomolies and not be problems at all or they can be a signal that something is starting to fail. The best thing to do is have the coeds scanned and see what temporary codes are present. At least this way you will have an idea what component is causing the light.

 

[beer]

Originally posted by: Evadman

Originally posted by: Elemental007

Originally posted by: LAUST
emissions

can be anything from a faulty O2 sensor to your gas cap not being on tight enough

In most cases, will it cause me to fail emissions tests? (non-CA)

Depends on how they check emissions. in IL you instantly fail if your check engine light is on.

Have any clue about Texas? My vehicle inspection is up for renewal next month I might want to have it taken care of on the 1st....in the event that it does come back on. I don't want to keep the problem-infested car more than another two years, but now I only put on <~200 miles a month, so it hardly seems worth it to invest in a new car until I'm out of college (may 2006)

 

[LAUST]

hit a Ford forum they might know.. or possible Chiltons online

 

[beer]

Originally posted by: Ronstang
Sometimes the feedback from sensors is out of range and trips the "check engine lihgt" yet goes back into range and eventually turns the light back off. These can be due to anomolies and not be problems at all or they can be a signal that something is starting to fail. The best thing to do is have the coeds scanned and see what temporary codes are present. At least this way you will have an idea what component is causing the light.

What sensors does it accept feedback from? (besdies the O2...which is the only one I know of)

 

[IshmaelLeaver]

It means a sensor has given a bad signal to the ECU. You could have a bad sensor, or have something actually wrong with the engine.

In some cases, the light will go off, but it doesn't necessarily mean the problem magically fixed itself. The code should have been stored.

 

[mjquilly]

usually either gas cap not on correctly, or bad PCV valve (easy cheap fix)

 

[Evadman]

Originally posted by: Elemental007

Originally posted by: Ronstang
Sometimes the feedback from sensors is out of range and trips the "check engine lihgt" yet goes back into range and eventually turns the light back off. These can be due to anomolies and not be problems at all or they can be a signal that something is starting to fail. The best thing to do is have the coeds scanned and see what temporary codes are present. At least this way you will have an idea what component is causing the light.

What sensors does it accept feedback from? (besdies the O2...which is the only one I know of)

Like 15 sensors. everything from Crank position to throttle position to coolent temp. heck there is even a sensor for knock detection.

A bad injector can set off the SES. there are 100's of codes. get it read for free.

I do not know how texas checks emissions. If it is just a tailpipe test it is possible to pass with SES on.

Oh, and SES = Service Engine Soon.

 

[SHoddyCOmp]

Originally posted by: Elemental007

Originally posted by: Ronstang
Sometimes the feedback from sensors is out of range and trips the "check engine lihgt" yet goes back into range and eventually turns the light back off. These can be due to anomolies and not be problems at all or they can be a signal that something is starting to fail. The best thing to do is have the coeds scanned and see what temporary codes are present. At least this way you will have an idea what component is causing the light.

What sensors does it accept feedback from? (besdies the O2...which is the only one I know of)

Read your manual?!? All sorts of little things, drive train, engine itself, look into it we dont have your car.

 

[mugs]

I've found the best way to get the check engine light to stop coming on is to take the bulb out. I know, I'm worthless too.

 

[Ronstang]

Originally posted by: Elemental007

Originally posted by: Evadman

Originally posted by: Elemental007

Originally posted by: LAUST
emissions

can be anything from a faulty O2 sensor to your gas cap not being on tight enough

In most cases, will it cause me to fail emissions tests? (non-CA)

Depends on how they check emissions. in IL you instantly fail if your check engine light is on.

Have any clue about Texas? My vehicle inspection is up for renewal next month I might want to have it taken care of on the 1st....in the event that it does come back on. I don't want to keep the problem-infested car more than another two years, but now I only put on <~200 miles a month, so it hardly seems worth it to invest in a new car until I'm out of college (may 2006)

Well, I'm from Texas so I have a clue about the emissions laws here. Considering that your car is a 1998 it is an OBD compliant vehicle but I'm not quite sure whether it is OBD I or II. OBD = Onboard Diagnostics. Anyway, since you have an OBD compliant computer system the smog check will simply consist of them hooking their computer to yours thru the OBD plug under your dash. If any codes are present in the computer that are emissions related either current or temporary then your car will FAIL, that is why I suggested you go get the codes scanned and find out what the problem is and at the same time have the person clear your codes and then drive for a while to see if it was an anomly or if it is actually a problem. The emissions test doesn't care......CODE = FAILURE....PERIOD, so go get it checked and stop asking computer geeks about your damn car.

 

[draggoon01]

instead of showing a "check engine" light why didn't they just make it display the actual code. then you can look it up in a book or internet. or is it just some conspiracy...

 

[Ronstang]

Originally posted by: draggoon01
instead of showing a "check engine" light why didn't they just make it display the actual code. then you can look it up in a book or internet. or is it just some conspiracy...

Then all the shops couldn't charge you ~$75 to read your codes, plus you cannot clear the codes without the scanner either so displaying the codes would be rather useless.

 

[KokomoGST]

Mebbe a dirty EGR valve... my dad hydrolocked my bro's Neon (cold air intake + 2 feet of standing water + father standing on gas while in water)

The EGR was so messed up that it was effecting the operation of the motor... so I told my bro to install an EGR blockoff plate (technically illegal in most states) and that made the engine run smooth again, but the CE light goes on since it checks for proper operation of that valve. If you have a gummed up EGR that's a possibility.