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Check Engine Light
The check engine light comes on in a car when the engine is experiencing a problem. Ask questions here about your car's check engine light.
7,238 Questions
What causes the engine light to come on in a 93 Ford Ranger?
There are a lot of sensors that can trip the engine light, you would have to scan it to know which one is causing the error
How to turn off the check engine light on a 1997 VW Golf?
THERE IS A RECALL ON PASSTS FOR THE YEARS 1992 THROUGH2002 LOOK UP RECALLS AND GET IT CHECHED ASAP!!!!!!!!!!!
Why would a check engine light be on?
The check engine light comes on and stays on when a problem is detected by the self diagnosis system of your vehicle. A flashing check engine light is an indication of a severe misfire or problem that is likely to harm your engine. Immediate diagnosis and service is needed. Generally, the problem is in the emissions or something that is affecting the effectiveness of the emissions, but other causes can trigger the light to come on, too.
To determine the cause, the vehicle will need to be taken to AutoZone or a shop that has an OBD2 scanner, or for 1995 and earlier models, an OBD1 scanner, While a scanner will not give you the magic answer, it will give you a code that narrows down the problem area. Or you can buy a handheld computer called a Diagnostic Code Reader that will do the same thing and may be cheaper. Plug the tester into the OBDII port inside the car. You'll find the port under the dash to the right of the steering wheel column. Many auto supply stores will loan you the test unit at no cost or will run the test for you.
Some specific causes for the check engine light to be on are:
- Gas cap left off, not tightened, not installed correctly, or needs to be replaced
- 02 sensor
- Engine misfire - error might clear itself after 3 complete warm-up cycles; not restarts, but warm-ups
- Problem in the emission system, including clogged exhaust or the catalytic converter not functioning properly
- Dirty/clogged air filter
- Dirty MAF sensor
- faulty sensors in exhaust system
There are pages and pages of items that can cause a check engine light to come on. Having it checked with a scan tool will narrow down the problem area.
More comments from Answers.com contributors:
- Not all systems are able to be read by your local auto parts store. For '95 and earlier cars, OBD I is used and can NOT be read by AutoZone or Advanced Auto. A simple paper clip can be used to jump 2 ports on the diagnostic port and have the Engine light flash a certain sequence. This will then tell you the code to refer to for troubleshooting.
- First rule of thumb is to check your gas cap; if it has been screwed on wrong, that will cause your light to turn on. Second, check your engine oil, you might be running low. Next, take it to a mechanic because it could be something worse. It could be anything; broken sensor, engine problems...take it to a mechanic you trust. Or if you still have warranty, take it to the dealer.
- The "check engine light" is by far one of the most misunderstood technological advances by the public. I am sure I will revise this as time goes on as it is an in-depth understanding for the public. It is a warning light that is illuminated when there is a problem with the EMISSION SYSTEM only. Emission system being the pollution control system. Don't get a hard on against it as it is a good thing once you understand it. One point that was brought up a a recent meeting of technicians was that the amount of hydrocarbons is greater when the gas cap is left off than when the engine is running. Hydrocarbons are part of pollution emitted as gasoline evaporates. Going a step farther, one facet of the emission system is the "Evaporative" portion. This is when the fumes from the gasoline are leaking from the system into the outside air. This is one part of the emission system that can trigger a check engine light. I would say that about 7% of the vehicles that have a check engine light are the result of a loose or inadequate gas cap. But understand that many scenarios are possible with the "check engine light" The vehicle's powertrain computer (note that some vehicles have 17 different computers) will run a series of self-tests. They will only run under certain criteria. And they can be vastly different from manufacturer to manufacturer. Some self tests are not run until preceding ones have run successfully. So if there is a problem in one particular area that is preventing another self test from running, you can have a situation where one problem is fixed, but another still exists. If you fix a problem and drive the car through a drive cycle that sets the monitor (or self test) the light will go off as it passes that criteria that triggered it in the first place.
After 1996, the auto industry went to a idea called OBD II (on board diagnostics). This was to get all the manufacturers onto a similar plane for troubleshooting and powertrain control. While they still differ vastly, many corrections and adaptations were made for technicians to better fix the check engine light problems. Prior to this there were so many different and poor troubleshooting data from a check engine light problem that resolving the problem was much more difficult. Many early warning light of this nature were set to illuminate based on mileage. An Oxygen sensor was one of the things that were meant to be replaced when that mileage was hit. This is much like many current "Change oil lights", that are set based on a preset mileage.
- Check engine lights involve the engine's electronics and/or electrical system, since they are interrelated. My '97 Sable's recent check engine light signified a problem with the camshaft sensor, which had to be replaced. Important, since it works with the ignition system, and while AAA is good to have, I hate being towed. It's a tricky repair, and like most manufacturers, Ford has the system designed to mandate a particular repair tool that's expensive to buy. The job's a pain anyway, and can be tricky, so it's best to have a certified mechanic you trust do it (I do not, repeat, do not, like dealerships for a variety of reasons). Never ignore a check engine light; generally easy to computer diagnose (but prepare to pay for an hour of diagnostics). All dash lights are potentially bogus -- sometimes these things take on a life of their own, signifying nothing, but it's foolhardy to assume that. Hope this helps.
Does a Crown Victoria have a V-Tech engine?
You want to know if a Crown Vic has a V-Tech engine? V-Tech is a trademark name of Honda Motor Company, and is a 4 cylinder engine. So the answer is no. After I thought about it for a while, I realized you might have also meant Vortec. Again the answer is no. Vortec is a trademark name of General Motors. So you will find a Vortec only in a GM product, not Ford. it has a v8 engine which is V- tech too.
How do you reset change engine oil light on 1999 silverado z71?
Turn your key to on position (not start).
Immediately depress the gas pedal fully (floor it) three times fast.
Watch the light, if you do it properly after a few seconds it will flash a few times and go out. Sometimes you have to do it a few times to get the timing right.
NEW ANSWER: That is almost right. But here's what you do. Turn key on do not start then push the gas pedal all the way to the floor 3 times being sure to let all the way off of it each time then turn the key OFF and then start the engine. You have about 5 seconds to do all of this.
If you were successful the light will flash 5 times.
How do you reset service engine soon light on a 2005 Mitsubishi Endeavor?
The owners guide for my '04 Endeavor says do not disconnect the battery I think, or the on board diagnostic record will be lost. maybe this would also clear the service engine light?
Probably not. The o2 sensor will become very confused! FriPilot
How do you reset the check engine light on a 1998 ford contour?
Easy, fix the problem that caused the light to come on in the first place.
Sounds like in your attempts to change the distributor, you altered the timing. that would explain misfires and car idleing to stop.
You can try cleaning it, but in general, most people have found that it needs to be replaced.
Although it is probably too late for this particular user, I recently searched and searched for an answer to the same questions about the p0401 in the late 90's Sable (Taurus)
Mine is a 3.0 24 valve Duratec. I am not sure about the process for any other models.
tools required:
- throttle body cleaner
- paper towels
- hard metal wire
- socket wrench and a 5/16, and a 10 millimeter deep well
- digital camera
- patience
OK: Here goes. Before you do anything else, do not buy any parts, whatsoever. Get to Autozone...buy some throttle body/air intake cleaner. Detach your negative (most likely black) battery cable (unless you owners manual suggests otherwise) Take a digital picture of how your throttle body looks before you start taking it apart. You will need to know where the various springs reattach.
Get yourself a socket wrench, with a 5/16ths, and a deep-well 10 millimeter socket. Take off your air cleaning tube, and make sure you are certain which hoses reconnect to where. once it's off, you'll see a brass plate inside the exposed hold. That is called the throttle plate. There is a lever to the left side that controls when it opens and closes, this lever is attached to a series of springs and a steel cable (the throttle cable). Take off the retention plate for the throttle cable (it will also be valuable to remove the throttle cable from its place, so that you are sure that you have not stretched it out in any way). Then, whip out that 10 mil deepwell, and take off the 3 bolts and one post screw holding the throttle body on. Yes, you are going to clean it, but that comes later, never mind that sticker on the top of the opening that says 'do not clean throttle body,' you won't hurt anything.
Take off the throttle body gasket, and do not break it, you will need it later. If it needs scraped off, take a picture of what it looked like for a reference, a discount auto parts store will try to sell you the wrong one, i promise. and that is a whole can of worms in a different story.
When you look inside the area revealed by removing the throttle body and gasket, you will see the air intake manifold. See where the egr valve is, looks like it goes into the manifold, right? No, none of those holes that are actually inside the manifold lead to it. Instead, on the face of where the throttle body mounted to the manifold, there is a c-shaped passage-way that has 3 opening that would allow air to bypass the throttle body gasket. remove the egr valve (10 mil as well) and get your piece of hard metal wire. you will have to make a 90 degree turn inside the egr passage to find where its outlet is, but, if you can't get the wire through, that is what is causing your p0401. remove that valve on the top of the air intake passage way (it's your idle air control valve, and you can't go liberally spraying throttle body cleaner into if or you will burn our the little motor at the end). in either case, whether it is completely clogged or not, place a paper towel underneath that c-shaped passage (it took me a while to figure out what people were talking about, mine was solid-black, caked completely with carbon, I didn't even realize it was supposed to be an open channel!!) completely douse it with the throttle body cleaner to break it up a little, and proceed to clean it out with your hard metal wire (a tiny, flat screwdriver might also be helpful, but be careful the cast mold of your air intake is aluminum, and will scratch very easily) repeat as necessary until it is clean, and make sure the passage is open leading to the egr valve (top left of the C).
Now you can clean out your throttle body itself. I found it easiest just to spray some cleaner in it, and let it sit. You do not want to scratch the inside of the throttle body. the cleaner, and then a good wiping with some paper towels will do the trick. Get back to Autozone, and bring the throttle body gasket (or picture of it) and order a new one, make absolutely certain that they are the same...remember, can of worms. you don't want what happens with the wrong gasket, it is unbelievably stressful to have your mercury sable station wagon sound like it is ready for the Indy 500.
replace all the parts, referencing the first digital pics you took to ensure it's all assembled properly.
I would suggest (although it is not necessary) to leave off the clean air tube overnight, and prop a brick on the gas pedal to open the throttle plate, it will allow all the acetone and alcohol from the throttle body cleaner in the a.i. manifold to evaporate.
Reattach the clean air tube (if you haven't already) and then reattach your neg. power cable. Start her up...and listen to that kitty purr. just kidding, for a while it will run strange, and unbelievable amounts of smoke will pour out. that's the carbon you cleaned up and the throttle body cleaner burning off. don't stress. Let it idle for a while. An extended strange idle means something went wrong, either a vacuum leak (bad gasket, you could have not reattached a hose)
If you took off you neg battery cable, you will find that your SES / CEL light has been reset and is now off. Don't be too confident, this could have only been one of your problems. Drive it for a day or 2, and see if it comes back on. if you get another p0401, then it is 75% certain to be your dpfe sensor. It's back, behind the throttle body, under the a.i. manifold, on the drivers side of the engine. You'll need that 5/16th and alot of blind groping to get it off. The new sensors are shaped differently, so you will also need to get new hoses (which is probably a good practice anyways). the 'ref' hose will need to be at least an inch longer than it was with the factory dpfe sensor.
happy times, hope this helps someone.
I'd bet you anything it has nothing to do with your egr valve. Hope you didn't waste the cash on a new one yet. Most often a new dpfe sensor does the trick. But in the Fords, depending on the engine, there is also a passageway that clogs up within your intake manifold. If your egr valve mounts onto the front of the intake on the drivers side, i would take the throttle body off and look just in case. If there is excessive carbon build-up, clean it out with some throttle body cleaner, and it might help your problem. Cheap fix, if your patience isn't considered an expense. Good luck. the dpfe sensor might run you 20-30 bucks, and a new throttle body gasket is 99 cents.
AnswerIt means the PCM sees a lack of EGR valve flow. That could be a problem with the EGR, EGR passages, EGR control system, EGR position sensor, wiring, or PCM.60% of late 90's early 00's ford and mercury p0401's are a bad dpfe sensor. 30%are a clogged egr passage after the throttle body in the manifold. 9% are either the valve or the evr vacum. that leaves 1% to be either a leaky hose, or a pcm. check again before you drop bookoo bucks on a pcm
good luck
mb
It has to do with DPFE sensor circuit high voltage detected. EGR temp sensor malfunction. That is all I can find. Hope this helps.
I found this: P1401 Differential Pressure Feedback EGR Circuit High Input
It is fairly common for this to be a problem with the sensor, not the EGR valve. The message is misleading. Also, it there is a 1400 message with it, it is most certainly the sensor, not the valve.
jcjimz
The advice above about the passage from the EGR to the throttle body is good. Usually you don't have to replace thr EGR but if you're taking it off replace it any way, it's not expensive. On the 3 liter DOHC Ford, Mercury engines the problem with the EGR is most always the passage through the manifold to the throttle body. Take off the EGR and the throttle body. From the EGR the port makes a hard right to the throttle body that you can not see. On the throttle body side there is a C shaped groove that is on the left of the main large port. It is probably full of carbon. Get a spray can of B-12 Chemtool and clean it out. You will see on the upper side of this groove that there is a small port. This goes to the EGR. Take your B-12 and clean the entire port then spray it into the port to the EGR. Let it sit then spray it again. Take the hose from the B-12 and spray it from the EGR side too. Let it soak. Do this until you get a steady flow of B-12 from the EGR to the throttle body. After weeks of spending money and time replacing things this was the entire problem and have been told by a reputable mechanic that 90% of the time that's the whole problem.
Connect a diagnostic code reader to find out what's going on. That's the only way you'll know for certain. It could be something as simple as a bad air filter or oxygen sensor but the computer diagnostics will tell you what code has been stored.
Where is the fuel filter on a 1996 Geo Prizm?
My son had a 95 prism and he found the filter in the left rear wheel well use the open end wrenches be careful not to twist the fuel line.
it starts but the oil light stay on
How do you reset check engine light on Nissan altima 2002?
you can go down to autozone and they can check to see what the problem is and possibly reset it for free, or try undoing the negative terminal on your battery for about a minute
How is the check engine light reset on a 1988 B2200?
Disconnect the battery for 5 minutes. This should reset the light. It will however come right back on unless you have found and repaired the problem that caused the computer to set the light in the first place.
Why is check engine light on and reduced power light on for 2001 Isuzu Trooper?
My 2000 Isuzu Trooper does the same - the reduced power light comes on, often after a hard break, and then the vehicle won't go over 10 mph. The gas pedal sometimes stops working altogether; the check engine light has been on for a year.
The scanner checks produce up to 6 error codes intermittently. Resolving those issues doesn't solve the reduced power problem. I have replaced the throttle position sensor twice, and more other parts than I can name, including the central computer. Mechanics at two different repair shops each spent a week each going through every single wire to search for a short (I live in Mexico, where labor costs are cheap enough to make this possible, and mechanics don't charge if they fail to fix the prolem). After the second mechanic located and repaired a broken wire, my vehicle worked briefly. Today the problem returned.
Many people are reporting the same problem and some solutions in the discussion thread at http://www.automotiveforums.com/t343629.html.
Why does the service engine light come on?
Why my Check Engine light comes on? All modern vehicles have a computer or ECM (Electronic Control Module) that controls the engine operation. The main purpose of this is to keep the engine running at top efficiency with the lowest possible emissions. With today's strictest emission regulations it's not very easy to achieve - the engine needs to be constantly and precisely adjusted according to various conditions such as speed, load, engine temperature, gasoline quality, ambient air temperature, road conditions, etc. How it works: There is number of sensors that provide the ECM with all necessary inputs such as the engine temperature, ambient temperature, vehicle speed, load, etc. According to these inputs, the ECM makes initial adjustments adding or subtracting fuel, advancing or retarding the ignition timing, increasing or decreasing idle speed, etc. There is a primary (upstream) oxygen sensor installed in the exhaust before catalytic converter that monitors the quality of combustion in the cylinders. Based on the feedback from this oxygen sensor the ECM makes fine adjustment to the air-fuel mixture to further reduce emissions. There is another, secondary (downstream) oxygen sensor installed after catalytic converter in the exhaust that monitors catalytic converter's efficiency. Besides, there are few additional emission control related vehicle systems. For example, there is an Evaporative system (EVAP), designed to prevent gasoline vapors from the gas tank from being released into the atmosphere. It also contains number of sensors and actuators controlled by the ECM. The ECM has self-diagnostic capability and constantly tests operation of sensors and other components. When any of the sensor signals is missing or out of normal range, the ECM sets a fault and illuminates the "Check Engine" or "Service Engine Soon" light also called MIL (Malfunction Indication Light) storing the corresponding Diagnos tic Trouble Code (DTC) in the ECM memory. The same will happen if a mechanical component of controlled system fails. For example, if the EGR valve fails, this will also cause the "check engine" light to come on. Even a loose gas cap will cause the "check engine" to come on. The stored trouble code can be retrieved with the special scan tool by the technician. The code itself does not tell exactly what part to replace, it only gives a direction where to look for - the technician has to perform certain tests specific for each code to find the exact cause of the problem. Q: What to do if my "check engine" light is on? A: The simplest way is to visit your local independent garage for proper diagnostic. They have all the equipment and information needed to correct the problem. The problem might be even covered by the manufacturers warranty and they could tell you that. Q: Is it safe to drive if my check engine light is on? A: It really depends what code is stored and what caused it. In worst cases driving with check engine light may cause more damage to the vehicle. A car may even stall while driving. If your check engine light came on, I'd certainly recommend to visit your dealer or a mechanic as soon as possible, just to be on a safe side. Q: Will disconnecting the battery reset check engine light? A: Disconnecting the battery might reset the check engine light on some cars. However, instead of doing so, I recommend to bring your car to a independent garage for a proper diagnostic, and here is why: - not all cars will clear the code after disconnecting the battery - some problems, if not repaired in time may cause a serious damage and more costly repair. - disconnecting the battery will cause many other basic settings of the vehicle's computer to be erased (e.g. idle settings, fuel trim settings, transmission shift points, etc.) - the Readiness code will be erased, which may prevent your car from completing an emissions test. (Readiness code is an indication that certain emission control components have been tested) - the radio, if code-protected, may be locked after disconnecting the battery - the "check engine" light will come back anyway if the problem still exist. Q: can I pull the "check engine" code myself? A: Having an appropriate scan tool or software and some technical knowledge it's not so difficult to pull stored trouble code. OBD II connector located on the driver's side under the dashboard It was quite difficult before, since each car manufacturer had different code assignment and different diagnostic connectors and protocols. Luckily, In 1996 in the United States, a Federal Law came into force requiring all US-sold cars to be OBDII (the On Board Diagnostics system version 2) compliant. This means that all cars from 1996 on must be able to be diagnosed with generic OBDII scanner. The diagnostic connector is identical on all OBD II cars as well as its location - somewhere around the driver's place. Usually, on the left side under the dashboard. There is a number of scan tools and software available (see links below). However, the code itself does not tell exactly what part to replace. For example, the code P0401 reads "insufficient EGR system flow", but it could be a bad EGR valve, clogged EGR passage or, for example, a faulty DPFE sensor (Ford F150 common problem) - there is a specific test procedure to be performed to pinpoint the problem part. Where to find specific test procedure - read below. Q: My car has the code P0133, how can I clear it? A: Code P0133 reads "Bank 1 Sensor 1 circuit slow response"; meaning the front oxygen sensor (located before catalytic converter) has slow response time to the changes in the air-fuel mixture. Unless there is a problem in the wiring or an exhaust leak, replacing the oxygen sensor most likely will fix the problem. Q: What does the code P0102 mean? A: The code P0102 reads "Mass air flow circuit low input". There is a certain procedure to test Mas Air Flow sensor (MAF) for proper operation. When you bring your car to a dealer, they will perform this procedure to check if the sensor is faulty. Mass Air Flow sensor failure is very common. Q: I have Ford F 150 with codes P0171 and P0174, is it the O2 sensor? A: Code P0171 reads "System too lean (Bank 1)" and code P0174 reads "System too lean (Bank 2)" What it means is that the engine is running lean. There are many possible problems that may cause the air-fuel mixture to be lean: Defective or contaminated airflow sensor, intake vacuum leak, dirty fuel filter, etc. There are certain tests to be performed to find the exact cause of the problem. Common problems with Ford engines are defective airflow sensors and vacuum leaks. As of my knowledge, Ford issued Technical Service Bulletin on this problem, you can check it at Alldata DIY. There is a website that for a fairly small fee provides instant access to vehicle-specific repair manual. It's called Alldata DIY - I use it quite often and found it very helpful. Besides "Check engine" trouble codes and corresponding test procedure, it also contains all kinds of diagrams (vacuum diagrams, serpentine belt diagrams, wiring diagrams, etc.), repair instructions, specifications, fluid types, maintenance schedule, component location, and a lot more. You also can find recalls, service bulletins, price for certain parts and labor, and information about how certain vehicle component or system operates. It's very similar to the information system the car dealers use. Whether you have your own small auto repair shop or Do-It-Yourself minded the information they provide would be equally useful. For more details follow this link: Where to get auto repair manual? Where can I buy an OBD II scan tool or software There are many different scan tools and software available on the Internet, from simple OBD II code readers to sophisticated scan tools. For example: OBD-2.com - OBD 2 software that turns your PC into scan tool. the service engine light comes on when a sensor is bad or the engine has an internal problem, you can try to disconnect the battery for about ten minutes and then hook it back up, if the light goes out then good and if it comes back then it needs to be decoded by a mechanic to find and fix the problem. they sell decoders at auto parts stores and i think schucks will do it free in the parking lot Pull the codes from the computer, match the code to the troubleshooting procedure, follow the procedure to find the source. Repair the source, light will go out if that was the only problem. There are "monitors" or self tests the computer runs the car through a drive cycle, if a problem occurs, it may not run all of the self tests until that problem is taken care. Therefore, another problem may exist. It is emission related. OR hook up a scanner that is capable of clearing codes, and hope that none are still active. The " check engine light" is by far one of the most misunderstood technological advances It is a warning light that is illuminated when there is a problem affecting the EMISSIONS of the vehicle.. Don't let it bother you as it is a good thing once you understand it. One point that was brought up a recent meeting of technicians was that the amount of hydrocarbons is greater when the gas cap is left off than when the engine is running. Hydrocarbons are part of pollution emitted as gasoline evaporates. Going a step farther, one facet of the emission system is the "Evaporative" portion. This is when the fumes from the gasoline are leaking from the system into the outside air. This is one part of the emission system that can trigger a check engine light. I would say a small percentage of the vehicles that have a check engine light are the result of a loose or inadequate gas cap. But understand that many scenarios are possible with the "check engine light" The vehicle's powertrain computer (note that some vehicles have multiple computers aside from the powertain computer) will run a series of self-tests. They will only run under certain criteria. And they are different from manufacturer to manufacturer. Some self-tests or
if it wont run when it gets warm it might also be a faulty crank sensor. and it wont always trigger a check engine light mine didn't, well it did but it threw a code for an egr valve so I wasted $220 replacing the egr valve to discover the problem was a $20.00 crank sensor. Have you checked the air filter? Sometimes an old air filter will cause problems that show up as a faulty map sensor.
Have the codes read, and fix the cause.
May be the rear axle speed sensor.
What wrong with your 93 Ford Taurus sho the check engine light come on after driving awhile?
Check your sensors.
Why did the check engine light come on out of the blue on 2002 Jetta GLS?
Get a code scanner for that vehicle and read the code. There is no way to figure out what's wrong without that information. It could be a MAP sensor, oxygen sensor, or any number of things that won't stop the engine but can make it run less efficiently. The computer will tell you what's wrong.
How do you reset the service engine soon light on a 97 sentra GXE with a 4 cylinder engine?
Pull the codes from the computer, match the code to the troubleshooting procedure, follow the procedure to find the source. Repair the source, light will go out if that was the only problem. There are "monitors" or self tests the computer runs the car through a drive cycle, if a problem occurs, it may not run all of the self tests until that problem is taken care. Therefore, another problem may exist. It is emission related. OR hook up a scanner that is capable of clearing codes, and hope that none are still active. Disconnecting the battery can create other headaches and will not likely solve your dilemma. Best bet is to contact the local snap-on dealer and have him refer you to a known good shop that specializes in this technology-he will know. The " check engine light" is by far one of the most misunderstood technological advances by the public. This is an needed in-depth understanding for the public. It is a warning light that is illuminated when there is a problem affecting the EMISSION SYSTEM only. Emission system being the pollution control system. Don't get a hard on against it as it is a good thing once you understand it. One point that was brought up a a recent meeting of technicians was that the amount of hydrocarbons is greater when the gas cap is left off than when the engine is running. Hydrocarbons are part of pollution emitted as gasoline evaporates. Going a step farther, one facet of the emission system is the "Evaporative" portion. This is when the fumes from the gasoline are leaking from the system into the outside air. This is one part of the emission system that can trigger a check engine light. I would say that about 7% of the vehicles that have a check engine light are the result of a loose or inadequate gas cap. But understand that many scenarios are possible with the "check engine light" The vehicle's powertrain computer (note that some vehicles have 17 different computers) will run a series of self-tests. They will only run under certain criteria. And they can be vastly different from manufacturer to manufacturer. Some self-tests are not run until preceding ones have run successfully. So if there is a problem in one particular area that is preventing another self test from running, you can have a situation where one problem is fixed, but another still exists. If you fix a problem and drive the car through a drive cycle that sets the monitor (or self test) the light will go off as it passes that criteria that triggered it in the first place. After 1996, the auto industry went to a idea called OBD II (on board diagnostics). This was to get all the manufacturers onto a similar plane for troubleshooting and powertrain control. While they still differ vastly, many corrections and adaptations were made for technicians to better fix the check engine light problems. Prior to this there were so many different and poor troubleshooting data from a check engine light problem that resolving the problem was much more difficult. Many early warning light of this nature were set to illuminate based on mileage. An Oxygen sensor was one of the things that were meant to be replaced when that mileage was hit. This is much like many current "Change oil lights
How do you reset the check engine light on 2001 Hyundai?
THIS WORKS!!!!!! It will work for all cars. Disconnect the both cables from the battery terminals. Hold the two cables together--in contact--for 10-15 seconds. MAKE SURE you do not touch the battery terminals with the cables while you are touching them to each other. [The first part of the next sentence makes no sense whatsoever.]This will drain the remaining battery in the cables themselves and it clears the computer. Simply reconnect and wah-lah. fixed. [I think the writer means that holding the two battery-cables in contact will drain the remaining "juice" in the cables, but that does not seem to me to be a correct description of what results from holding the two cables in contact with each other for 10-15 seconds.]
[touching the cables together will short the cars entire electrical circuit, clearing any charge held in the computer systems. Some cars may require the key to be in the accessory position. DO NOT DO CROSS THE CABLES IF THE CAR IS RUNNING. Also, do not do this if your car has a second battery (this is found on some security systems and some European cars). Cars with such systems usually have a jumper that, when shorted, will reset the computer. If you are unsure if you car has such a system, please check your manual or take the car to a mechanic. NOTE: some cars may require a code to be entered into the stereo unit after disconnecting the battery. This is true on SAABs and BMWs, among others.]
AnswerCheck out the O2 sensors.might be bad, or not connected [off topic - this is a common problem but please answer the question]1999 Chevy Silverado check enigine light code read Cylinder 7 misfire already replaced obvious?
Check Coli, an wires attached to coli, coli my not be getting enough juice
Most are located behind the gauge cluster. You have to remove the trim and four screws to get to the little switch either by the spedo cable or lower right corner of the cluster. ( if this a 120,000 mile interval, remove the light!) REMOVE TRIM COVER FROM RIGHT LOWER DASH, YOU WILL SEE A SMALL SWITCH. USING A LONG SCREWDRIVER YOU CAN MOVE SWITCH AND RESET EGR LIGHT.
