Avoid Costly Auto Repairs If Check Engine Light Is On
90Is your check engine light on?
This article shows how to understand what your check engine light means, how to reset it, and how to avoid expensive repair bills.
If your check engine light is on and your mechanic says you need some expensive repair, there is an easy way for you to know the truth.
There are a number of component failures that turn on the check engine light. One of the most expensive is the catalytic converter.
Often it is nothing more than a faulty sensor that is triggering your check-engine light to come on.
Your car's computer keeps a record of the diagnostic codes that represent which sensor is reporting a problem. It might be the component itself that's malfunctioning, or it might be the sensor. When sensors fail, it is usually intermittent. Clearing the codes from the computer and watching to see if the check-engine light comes back on, is a useful experiment.
I'm going to explain how to read your car’s diagnostic codes and avoid an enormous repair bill by safely resetting your car's computer memory.
Your Car's Diagnostic Codes
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Since I have a background in computer science, I am aware of an important issue... The only way the car's computer can know if a unit is failing is by a sensor reporting back to the computer. Each sensor specifies a particular code.
When the computer has a code stored, the check engine light is lit to let you know. The computer registers a specific engine light code to indicate which sensor reported the problem. These codes are known as the OBD I and OBD II codes, but more on that in a moment.
Sensors Can Fail or Erroneously Trip
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It's very possible that the sensors can fail, or get stuck, and temporarily report a bad code. If you have a universal catalytic converter, these are known to erroneously trip the sensor from time to time.
Sometimes a sensor will break, and an honest mechanic will tell you that. Replacing a sensor is not that expensive. But what if you get stuck replacing an expensive catalytic converter?
There is a way to do your own cheap engine diagnostics.
So what is the catalytic converter anyway?
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Questions?
See common questions people are asking in the last section below, along with the answers.
The catalytic converter is part of the automobile exhaust system, placed between the engine and the muffler. It reduces the toxicity of emissions from internal combustion engines.
First introduced in the U.S. in the mid-1970s to comply with EPA regulations for controlling auto exhaust, its functions are monitored today by the car's computer system with sensors on all important auto parts. If the sensor detects a problem, the check engine light will light up.
Replacing the catalytic converter can be pretty expensive for parts and labor combined. And if you are scheduled for your annual State Inspection, then you will be forced to pay for the repair, in order to pass the inspection.
I once had this problem, and I knew several friends who also got stuck with an expensive repair bill when their check engine light came on.
The catalytic converter typically has a warranty exceeding the rest of the automobile's warranty length. But if you fall outside of that warranty period by time or by mileage, and if you are in a state that implements vehicle emission inspection programs in your area, then you could be facing a large repair bill, especially if you are stuck with needing it repaired quickly, due to failing a state inspection.
You can avoid replacing catalytic converter. In many cases it is just a bad sensor and you wouldn't know that unless you have the ability (as I will explain) to clear the car's diagnostic codes and watch to see if the check engine light comes back on.
The Diagnostic Code Scanner Tool
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Many times I have noticed the mechanic plugging in a code scanner under the dash to read the engine trouble codes from the car's computer. I thought how nice it would be to know what the computer has to say about a check engine light on, before I go into the repair shop. So I decided to spend a little money on my very own Diagnostic Code Scanner.
I did a few searches for these units and found really good prices and a large choice of models on Amazon. Prices range from around $50 to the upper $200's...depending on the model. Each model offers different features. After a little review, I realized that I didn't need to buy the most expensive one.
If you have a 1996 or newer car, then the cheaper models of Diagnostic Code Scanners will do just fine. All cars since 1996 use the OBD II codes. The more expensive Code Scanners can read the older OBD I codes as well. That is simply not necessary to have, unless you have a really old car.
Reading Trouble Codes - Take a moment to view this useful video:
The Scanner I Use...
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Actron Diagnostic Scanners
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I purchased an Actron Diagnostic Code Scanner with On Screen Definitions for OBDII Vehicles.But there are newer ones available now in auto parts stores and on Amazon.
This thing works great! It has a display screen that lets you flip through a menu of options to read the computer for any pending problem codes, read the status of the individual sensors, and even determine if the check engine light is on when it should be off, or visa versa.
There is no need to look up the codes in a table either, since it shows the description of the codes on the screen. It also lets you reset the check engine light by clearing the codes from the computer.
Most diagnostic scanners offer similar features. Actron has versions that also read OBD I codes in older vehicles with an optional cable.
By reading the codes myself, I was able to see that my problem was indeed the catalytic converter. But there is no way to know if it really is a faulty sensor. At least not right away.You need to erase the code and then see if it comes back on over time.
How to Erase the Check Engine Light
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Each code scanner is different but they all have a function that allows clearing and resetting the computer.
You may not have to read it's user's manual although I recommend you do. The scanner will probably guide you through the process on it's little screen if you just carefully follow along with the on-screen prompts.
The scanner I used has a menu of options. I first chose the option to scan for any trouble codes that might be in the computer. It also shows the meaning of the code in simple English. Very helpful. Then I chose the option to erase the codes it found. Done!
But wait ! There is an important next step before running in for an inspection.
System Ready Status After Erasing Codes
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So I cleared the codes from the computer and the check engine light went off, as expected. When you clear the codes with the "Erase Codes" function the status of the System Monitors is set to “Not Ready.” If you were to bring your car in for an inspection the mechanic would tell you that they can't pass the car at that time.
You have to drive 50 to 100 miles in several individual trips until the system reads the status of all the components again. "Several trips" means that you shut off the engine and start another trip. So it's not just 100 in one trip. It's more like doing three trips of about 30 miles each. Then you can connect the scanner and let it read the System Status to see if the "Not Ready" condition is gone.
There are three conditions to understand with the System Status...
- System Status is READY and the check engine light has not come on. The system is working properly and your car will likely pass emissions tests.
- System Status is NOT READY. Your car has not been driven enough and needs to be driven until the system monitors record a READY condition.
- System Status is NOT APPLICABLE. You may see that indication for some components. It means that your car does not support that status monitor and you don't need to be concerned about it.
After you reset the codes, either of two things will happen. If the "Not Ready" status becomes "Ready" and the check engine light did not come back on, then the problem may have been an intermittent faulty sensor. Or if the check engine light does come back on, then scanner will show you that bad codes again and that would indicate that you do indeed have a component failure as specified by the code. In that case at least you'll know you will be spending money to fix a real problem.
In case you are thinking that I blew the light by turning it off, that is definitely not the case. First of all, the Diagnostic Code Scanner checks the condition of the check engine light as well. And secondly, when you turn on the ignition without starting the engine, all the panel lights light up as a test. So I can see that they all are working.
I had saved a few friends already from this potentially expensive fate, with my Diagnostic Code Scanner.
Conclusion: Getting your own Diagnostic Code Scanner can save you from a mechanic telling you that you have a major problem which may just be a result of a faulty or tripped sensor.
New Safety Monitoring Standards - Tire Pressure Monitoring
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Diagnostic Tool for Tire Pressure Monitoring Systems
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In 2008 the National Highway Traffic Safety Administration introduced a new requirement that all new cars and light trucks must have a Tire Pressure Monitoring System, known as TPMS.
These newer cars and trucks have a TPMS warning light in the dash, which will come on if the pressure on any of the tires is bellow 25% of the recommended pressure. A flashing or blinking TPMS light means that one of the TPMS sensors is malfunctioning.
The TPMS codes are not included in the ODB I or II codes and will not be recognized by an OBD scanner. A company named Autel makes a scanner specifically for the purpose of reading the TPMS codes, as shown at the right.
This scanner displays diagnostics results of Sensor ID, Tire Pressure, Temperature, Battery Condition and OE part number. Unlike the method of reading the OBD codes, no physical connection is required to read the status of the TPMS. It reads the data via wireless signals.
Common Questions You Might Be Asking (Updated Oct 2011)
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Here are common questions people are asking about this topic along with my answers...
Does the check engine light eventually turn off without fixing the problem?
If the problem is not due to an actual component, but rather just a faulty sensor which is intermittent, then you may notice the light goes off after some time. But it may come back on again once is a while if the sensor continues to send faulty signals. It's best to have a mechanic look at it, but tell them that it seems to be a faulty sensor so they know you already have some knowledge of the situation.
I know two friends who paid dearly for a new expensive part, only to have the light come back on weeks later. The mechanic refused to refund the cost, stating that he had no way of knowing it was only a bad sensor. Don't fall for that.
Is the catalytic converter connected to the car's computer?
Yes, that's one of the parts that is monitored by the computer. If the Catalyst System Efficiency is below threshold then It registers error code P0420.
Can the Actron scanner read individual sensors?
Yes, it will read all sensors and display the results. Then it let's you optionally clear the codes from the computer to start fresh.
How many miles need to be driven to reset check engine light for inspection?
After you clear the computer you need to drive up to 100 miles to give it a chance to monitor all the sensors and register the results. Sometimes it may be complete in about 50 miles. You'll know when you connect the scanner and check the status. It tells you if ready or not ready. Wait till you see everything ready before going for an inspection.
If you clear check engine codes with a scanner will it allow you to pass inspection?
If the problem is a faulty part, chances are good that the computer will read a new error and register a code again by the time you get into the shop for the inspection. The purpose of this article was not to cheat the system but to avoid costly repairs when only a sensor is at fault.
If it's only an intermittent problem with a sensor, it may take a while for the sensor to get stuck again and you will pass inspection. Unless the sensor is so bad that it registers a code again before you get your car inspected. In any case, remember to wait until the computer registers "ready" as I mentioned in the last answer.
If I reset my light will it show up in state inspection?
As long as you wait for the computer to show a "ready status" then there will be no clue that you reset the computer. See my prior answer about how many miles to wait.
I got a new catalytic converter and my check engine light is still coming back on. Why?
When the check engine light comes on and the scanner code shows that the catalytic converter is the cause, it could simply be the sensor that failed. That's why I recommend using your own scanner to clear the computer and see if the light comes back on. If the sensor is faulty, it may be intermittent.
When a car mechanic reads the code, they'll most likely sell you an expensive catalytic converter when all you needed was a new sensor. There is no way for them to know without clearing the computer and waiting to see what happens.
Is it possible that it could be a loose gas cap?
A loose gas cap causes a fuel vapor leak sensor to register code number P0455 and the check engine light will come on. But this code may be indicating a more serious problem. You could have damage anywhere in the EVAP system, which captures and returns the fuel vapor. So, by all means, make sure your gas cap is tight. And if it's seal looks damaged, get a new gas cap. But if the light continues to come on and your scanner shows P0455, then get it checked out.
Have some fun, test your knowledge with the quiz below. And if you found this article helpful, please rate it with the buttons below. Thanks.
Copyright © 2009 Glenn Stok
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The author, Glenn Stok, also writes articles on business and relationships, consumer electronics, social issues, and inspirational philosophical discussions.
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Reader Comments (Most Recent First)Loading...
Hi I bought a Volkswagen golf but to pass my emissions test had I buy a new cat in January when I put that in the engine light came on and I had to eventually replace both sensors however the light still comes on I have taken it to a mechanic and he has told me it has to be a dodgy cat so am getting a new one even though the one I have was only purchased in January is this right or is there something else wrong
Manny, I am not an expert in this area. But my guess is that if you can't read the mileage it means it was tampered with. I personally would never buy a car under those conditions as it could never pass an inspection.
Hi . I have a mercedes 2000 c280 emissions failed it because of a bad air mass sensor. I took it to get retested and they wouldnt test it because they couldnt read the mileage on the dash . I bought the car 6years ago and the cluster was already like that. Couldnt read miles ,temp or clock doesnt work. Is the emissio ns inspector giving me a hard time
Kristina, Since you had a new catalytic converter put in and the light still keeps coming back on with the same code, that unfortunately means that it is a bad sensor or that the shop gave you a defective catalytic converter.
Did you buy a rebuilt one or a new one? Did they replace the sensor too, just to be sure. The ready status occurs about 100 miles after you reset it.
Maybe you can squeeze in the inspection after you see that your scanner shows "ready" and before the light comes back on. But go back to your mechanic and as the above questions in any case. Good luck.
Hi Glenn! Thanks for the informative article. I have a 2002 Monte Carlo SS and my CEL keeps coming back on with the P0420 code. I borrowed one of the Actron diagnostic scanners you mentioned from a friend, and have cleared the code 3 or 4 times already, but it keeps coming back on.
The thing is, I had my catalytic converter replaced in October! The code first came back on not even a week after the replacement, and has done so every time I've cleared it. I would be fine with it, but I still have to pass my VEIP test for MD state inspections and the last time I went in I got a not pass/not fail, which I'm assuming is because of the Not Ready status you mentioned from clearing the code myself.
Is there a reason the same code would come back immediately after I had the issue resolved?
Thanks!
Jacob Roberts, I discussed that in my article. The computer gets reset back to ready status in less than 100 miles. Not 500. But your mechanic should have shut off the light. If you paid $350, ask him or her to do that. Or get your own code scanner such as the one above for $20 and turn off the light yourself. Then drive about 100 miles and check it again for ready status. More details are in this article.
After $350 repair (replacing the EGR Valve). My Check Engine light was out for only about 5 miles, But it's back on again. called back the mechanic and said that I have to drive the car 500 miles for the engine light to go out, thats how long it takes for the computer to reset. I need to smog this car. This is unacceptable. That's mean I have to drive out of state. FIVE HUDRED MILES? really? is that true?
Jan, Any business has a right to charge for service. Connecting their code reader to your car and reading the code is considered a service. But you can do it yourself if you have your own code scanner. If they told you the cost of the service and you agreed to have them do it, then it is acceptable.
Hi again,
Yes, I see that now - but I didn't find your fabulous article until I was Googling to find out if I was ripped off or not (and if I should complain and ask for a refund or a credit).
So, is it legitimate to charge a code reading fee? Or was I "hosed?"
Thanks,
Jan
Jan, For less than that $50 you paid for a one-time reading, you could have purchased your own code reader such as those shown in this article.
Hi Glenn,
Thanks for all the great information. I just had my Trailblazer inspected (the Check Engine light was on), and had to have a thermostat and sensor replaced. When all was said and done it was $398, and that included the $37 inspection fee (which we expected), and a $50 "Code Reading Fee" for hooking it up to the computer - which was totally unexpected. Is that legitimate or is this guy a thief?
Thank you,
Jan
Daria, I would trust that last mechanic who you mentioned. It's true that if the light doesn't come back on then you should be fine.
The dealer said I had code P0711, transmission fluid temp sensor performance out of range, tested sensor and verified failure. They reset it (back in December). The light has been off since then. The CEL came back on Saturday, and I put gas in today (Monday), and it went out. How do I know that it isn't just a gas cap being loose and not something with the transmission? I am looking at repair cost of over $500 if the dealer is correct, but how do I know they are being truthful? It has been on one other time, and it seems to happen around feuling times...so I am thinking it's just a loose gas cap....what do you suggest I do? One mechanic (not at the dealer)told me if the light didn't come back on, or I didn't notice any issues, not to worry about it. Who do I trust? Thank you!
Bob, P0601 means the computer failed a self test. This can also be caused by bad wires running to it. Or grounds on an sensor may be bad if they became rusty. If you do buy one, make sure it includes a warranty. Rebuilt PCM's are not always reliable.
Hello Glenn. I have a 2002 Dodge 1500 2wd Pickup with a 5.9 gas engine. The check engine light is on and the code reads P0601 which indicates a ECM failure. The truck runs fine, however I need to get and inspection soon. I can order a new rebuilt ECM from AutoZone and have read the simple installation instructions. My concern is spending $250 and it not fixing the problem. Any suggestions or guidance?
Maria, as stated in my article, If the Catalyst System Efficiency is below threshold then it registers error code P0420. So if that is the code you are getting, your mechanic is correct.
I have a 2003 toyota corolla that i bought in 2002 it has 125,000 miles. my check engine light came one about a month ago and it read it was the 0xygen sensor i had that fixed plus the spark plugs here i am a month later and my check engine light came back on. i took it to my neighborhood auto zone and the guy who check my codes said it was reading code Po420. the guy at autozone told me that it might be the other oxygen sensor?. This time i took it to the mechanic and he is telling me i need a new catalytic coverter because its running under 80 percent. should i try changing the other oxygen sensor first? or should i change the catalytic coverter.
Chee, That's the idea. But I don't know if they would be willing to clear your codes. The best thing is to do it yourself. The cheapest $20 scanner like the one listed above is just as good and will also allow you to clear your codes.
Hi I have a 1998 Toyota Avalon and the check engine light just came on. You mentioned in the video to ask the service department if they can scan the code for free. Could I ask them to erase the code as well? If they erase the code, and then I continue to drive without the light coming on then maybe I can avoid a big repair. If the light does come back on, then I know that I should take it back and can invest in a more serious repair that is needed. Thanks.
Mary,
Have your mechanic clear the code again, or buy your own scanner like the ones listed in this article and do it yourself. If the light doesn't come back on so quick then maybe it's just a bad sensor.
You can also try putting high test gas in your tank (when empty, so you fill it up) and drive with high test gas just for the one time. This has been known to clear out the catalytic converter at times, and the problems will be resolved. It worked for me, and the light stayed off now for two years.
Hi Glenn,
I am a college student and I graduate in May. My Pontiac Grand Am's service engine light came on about two months ago. I brought it in to the mechanic and he said it was a 420 code. Now he reset the service engine soon light and it just came back on. Can I make it to May without fixing the car or should I spend the $700 plus to fix it?
Lindsay, This is exactly what I was saying at the beginning of this article. You never needed to replace either catalytic converter.
Since your light is still coming on, and assuming the mechanic told you his or her scanner showed it was a code for the catalytic converter, then it is obvious that it was only a sensor that was bad, as I explained in this article.
You can confirm the codes yourself if you get your own $20 scanner such as the one I listed above. And with that scanner you can clear the codes and see if the light comes back on. A lot cheaper than paying for two new catalytic converters.
Hello. A month ago I had an error code for the right catalytic converter in my 2005 dodge stratus. I had that fixed, then three weeks later I had another error code for the left catalytic converter. I have had them both replaced and the engine light came on again 10 miles down the road. I brought it in and they said they forgot to reprogram it and tell it they put a new catalytic converter in. So I thought I was done with the deal, then I left and it came back on! What the heck is going on? I only have 40,000 miles on my car.
Amanda, It should have become ready after driving 100 miles. You may need to do that in three shorter driving sessions. Not all in one trip. If that doesn't do it, you may have some other problem. Your scanner will tell you which status is not ready.
My car had a code come up that basically said for me to change the gas cap. I changed it and a new code came up. P0171. Something about system too lean on bank 1. We cleared the light and have driven 200+ miles. I use my car every day to go to work & school. We went to get the car smogged and the tech said that it did'nt pass or fail. We have access to a machine to check it and it still isn't ready. What do you think is wrong? When will it be ready again?
LoLa, It will not damage the engine but the cat. conv. may overheat. So be careful about parking over leaves, etc. Just in case, you should try to find someone you trust to check it anyway.
Code PO420 has come up on our 2000 Astro Van. Had the Cat. Coverter replaced about 3 years ago but shop has now gone out of business. We are in Mexico and will return to U.S. in a few months but it's a 2000 mile drive home. Will driving with the PO420 code damage the engine? I have no access to a Chevy dealer in our small village.
Ernie, if all the lights are off, then it will pass the inspection assuming the computer is not showing any "not-ready" conditions left over from a previous code that may have cleared itself. If you want to know for sure before bringing in your car, get one of the code scanners and check the "ready status."
Hi Glen, I bought a used 2000 Nissan with 200,000 miles on it and it is almost time to be inspected but have had trouble with various lights coming on, Check engine, service engine soon, and the abs light all coming on at various times over the last few months. Since I am not having any engine trouble and the car runs fine, do I have the computer changed or just the sensors? By the way all of the lights are now off but I am afraid to try and get it inspected until I solve the light issue.
Professional Master Tech, I appreciate that you said it's unacceptable to you for someone to pay for an expensive repair only to have the light come back on. I wish there were more mechanics like you who people can trust. When I once brought my car in for a checkup with the MIL light on, the mechanic used a hand held scanner that did not support the data logging. He didn't bother to connect the PC scanner that I'm sure he had.
there are many parts to this article that are true, but some that are not. I can tell the person who wrote this article found most of the information from other resources on the net. That being said clearing a DTC (diagnostics trouble code) and waiting to see if the light comes back on is one way to determine if a sensor "glitch" is at fault, but you must keep in mind that in doing so and waiting for the MIL (malfunction indicator Light) to come back can result in further damage to other components. Thus causing more expensive repairs.Catalytic converters don't fail on their own. It is usually caused by excessive HC(Hydro Carbons aka fuel) entering the converter. There are also other reasons such as excessive oil consumption of the engine due to worn internal components, external impacts to casing that cause the sub straight to break free. Converters are not connected to a cars computer. The vehicles computer has inputs from a pre converter oxygen sensor and a post converter oxygen sensor. It uses these inputs to determine catalyst efficiency. The scan tool used by professional automotive shops have the ability to graph this information and allow a proper diagnoses on the repair. A 50 dollar code reader will not. Also keep in mind that when you clear a DTC you also clear any freeze frame data the computer has saved when the fault occurred. This data is very useful to a technician who is properly diagnosing a fault in the fuel and emission control systems on a vehicle.
My advise to anyone who has an engine light on is to take it to a professional technician who you can trust. A properly trained tech who is good at what they do will always advise you on the best repair and the least expensive way to go about it. Paying for an expensive repair to only have the MIL to come back on is unacceptable to me. I work in this trade and have been for 10 years. If the diagnoses was done properly the light should not come back for the same reason.
Rose, Thank you for asking your question. It's a very important addition to this article, as it explains what many people get into.
If your light is not coming back on after they cleared the codes from your computer, that indicates that your catalytic converter is okay.
These people sound like crooks to me for two reasons...
(1) They told you that you need to replace BOTH the catalytic converter AND the sensors. That implies that they already suspected that ONLY the sensors are the problem. And if they didn't replace them, then you would still have a problem, and they needed to hide that from you.
(2) The biggest give-away that they are crooks is that said your car will blow up. That is just silly and they think you are dumb and gullible, which you are neither. Stay away from that mechanic!
Now that you have your own code scanner, you can clear the codes yourself and watch to see if the light ever comes back on. If it is intermittent then it probably is only a sensor. Either way, emission problems never cause a car to blow up.
I am glad I found your website. I took my Nissan to the dealership after the Service Engine Soon light came on and I was told that I need a catalytic converter and 02 sensors which will cost $1500. I told them I would think about it. I had to $105 for the diagnostic test. Questions: Should I have gotten some type of printout from the diagnostic test? The engine light doesn't come on now. I guess the dealership turned it off. So after reading your comments that it is best to turn it off and see if it comes back on and then you know for sure you have a problem. Now I can wait and see. The dealer told me that my car might blow up when I drive it off the lot. Thanks so much for a great website. I have put your site on my favorites list.
My 99 4runner, that never had a problem before, began running rough, very rough idle, and no power uphill coming home from a funeral 3 hours away at night . The plug wires were about melted, and after that repair, the Toyota dealer said the code included the misfire and cat converter. He came up to me and whispered that the price for the part indicated was about 2000 bucks, he and another tech had checked and rechecked the price in disbelief, and then whispered that I could choose a muffler shop and get it done for a lot less there! He then told me where the 2 closest muffler shops were. It took 20 minutes and the bill was 180. So if you are needing a new catalytic converter, and it isn't just the sensor after all, check with a reputable muffler shop first! Thanks for this article. I am going to a parts store to get my husband's truck codes read and cleared since he also had the freaky gas cap which we replaced just before reading your suggestions. I now know from your posts how to wait for the notready to clear and see if the light comes back on. Thanks again!
Hi Glen. My original message and your reply is below.
I finally received my OBD 2 scanner. The Auto Zone guy was correct. The connector on the vehicle seems to not be working. The scanner didn't do a thing. I did tighten my gas cap as you suggested and that corrected the gas gauge problem. And that is probably why the Service Engine Soon light came on in the first place as you also guessed. However, now I know that the connector has a problem. I'll try the fuses and see if that works. Thanks again. I appreciate your help.
Sincerely,
Von
Von.A 8 days ago
Thank you for the article. Service engine soon came on in my 2001 Blazer so I took it to Auto Zone. Their scanner would not work on my vehicle. They said it might be a fuse. I remembered that I had accidentally started the engine with the gas cap off so I unhooked the battery to reset the computer. Drove it several times for total of 100 or so miles and the light is back on. I'm female by the way and don't know a lot about cars. Has anyone ever had a scanner not read out? My gas gauge has been acting weird too. I did purchase my own scanner from the Ebay link on this page and hope to eventually get a reading and avoid that costly catalytic converter repair. For $30.00 it was hard to pass up. :-)
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Glenn Stok Hub Author 8 days ago via iphone
Von, this does not sound like your cat converter. It sounds like your gas cap is not on tight. Simple solution. Check it.
Yea I was actually thinking the samething, it wont harm to just try it.
Well thanks a lot Glenn you have been very helpful
Andrea, The only way to find out is to get one of the code scanners above and clear the code from the computer. Then watch to see if it comes back on again for the catalytic converter. If it seems intermittent then it may very well be the sensor. But no way to know for sure without watching it over time after clearing the codes.
HI GLEN,
I OWN A CHRYSLER 300 2006, MY ENGINE LIGHT IS ON. I FAILED THE EMISSION TEST, AND A WEEK AGO IT TURN OFF BY ITSELF, AND NOW IT TURNED ON AGAIN, I TOOK IT WITH A MECHANIC AND THEY SAID THAT IT IS THE CATALYTIC CONVERTER, AND THE COST IS OVER $700 WAY TOO MUCH MONEY!
FROM YOUR ARTICLE I HONESTLY BELIEVE IT IS A SENSOR LIGHT. WHAT DO YOU THINK?
Al, the llight indicated that something is wrong. Get the $30 U380 Universal Engine Scanner on eBay (see above) and find out what it is.
my chech engine keeps on popin up and everything is ok
Matt, Your mechanic may be talking about another item or they are taking advantage of you. For the small price of a new gas cap and the small cost of buying your own code scanner, it pays to try that first. After using a new gads cap, clear your computer codes and watch to see if the light comes back on.
Hi Glen,
I had a P0455 & P1448 diagnostic trouble code come up when I went for my NYS inspection earlier today (Failed both the safety & emissions part of the test). Like you said earlier in an earlier post P0455 could be a faulty gas cap, do you suggest just buying a new one & trying it on? Perhaps the threads on my gas cap have worn out. I'm looking at atleast $1700 for repairs from the mechanic, do you think that's worth it getting all that repair work done for a 2000 sentra?
Von, this does not sound like your cat converter. It sounds like your gas cap is not on tight. Simple solution. Check it.
Thank you for the article. Service engine soon came on in my 2001 Blazer so I took it to Auto Zone. Their scanner would not work on my vehicle. They said it might be a fuse. I remembered that I had accidentally started the engine with the gas cap off so I unhooked the battery to reset the computer. Drove it several times for total of 100 or so miles and the light is back on. I'm female by the way and don't know a lot about cars. Has anyone ever had a scanner not read out? My gas gauge has been acting weird too. I did purchase my own scanner from the Ebay link on this page and hope to eventually get a reading and avoid that costly catalytic converter repair. For $30.00 it was hard to pass up. :-)
Hi Glenn
Just tried the scan tool again and it works fine. No problems driving the car and light stays off. So with some luck I may have got away with it. It's a mini cooper S (2007). Garage just replaced the O2 sensor and the light come back on. I got this scan tool off eBay just for piece of mind. Its a Vgate VS550 with code and explanation of the code Code (P0136) showed O2 sensor circuit bank 1 sensor 2.
Jim, This is the reason for reading instructions first. I can't tell you if you did any damage. That all depends on the type of car you have and the way the code reader you purchased works. The vgate is not one I listed in my article.
Hi. Came across this site while looking for information. Very interesting read. Perhaps you can help with my concern. I purchased a vgate reader to turn off the warning lite. I did this with the engine running. Then I read the instructions that said don't clear the codes wit the engine running. Whoops. Have I done any harm?
Minnesitta, it sounds like you are confusing your problem with emissions control issues. The error codes refer to emissions problems. I would get it fixed befor the warranty expires I'd I were you. It's a no-brainer sine it woun't cost you anything anyway under warranty.
Hi Glenn the check engine light came on in my vehicle, a 2008 Saturn Aura, and I took it to a local auto parts store and they checked the code for me and it said it had to do with the cam shaft position. After I left the auto parts store the check engine light did not come back on and I asked them if they reset it and they said no they are not allowed to do that but that the cam shaft can re-align itself if the computer senses something. Do you know if this is possible? Otherwise I will wait and see if it comes back on again but by then it may be out of warranty at the dealer and they won't want to fix it. Thanks and I've been reading this page it's very helpfull.
Glenn Stok Hub Author 3 weeks ago
Jason, I assume you mean a Dodge catalytic converter. I never heard of that. You have a VW, not a Dodge. Makes no sense to me. I would check it out with another mechanic.