Read engine fault code after it has been turned off?

Then you don’t live in a state that does pollution testing.
Light must work, and not be on when being tested.


Yes, thankfully we still have a shred of freedom and dignity here.

Auto manufacturers would not put a check engine light and corresponding sensors in a car unless they provide some value. The codes provide useful diagnostic information that helps keep the car running well. I would never buy a car that had a CEL lit. If the seller could not or would not fix it, that speaks volumes to the balance of maintenance ignored on the car.


So you don’t maintain your cars, why do you want to tell others how to maintain their cars?


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Yes Mr. Texas does contribute quite well here . You are the one who thinks it is accetable to polute the air that we all need to exist .


The light being on drives me nuts. We don’t have emissions testing here, and I’m sure the purge valve solenoid being failed on my truck wasn’t harming the environment to any extent, but I replaced it merely because the dang check engine light is my mortal enemy! And I have defeated it yet again! :grin:

I have 3 cars, two are over 15 years old, all 3 have over 150k miles, and no cel. I admit I was defeated once by a tbi 350 with an egr related check engine light that I never resolved before I sold the truck. Check engine light wins 1. But so far I’ve won the rest!


I’m glad that you replaced that purge valve solenoid. In addition to the presence of the light being annoying, once someone deludes himself/herself into thinking that it isn’t important, he/she has no way of knowing when 2, 3, 4–or God only knows how many other–“new” codes have been set after the first fault caused the light to start glowing originally.

Several years back, we had a post from a woman who stated that…
My Suzuki’s Check Engine Light has been on for 16 years. What’s wrong with my car?



I have more cars than that, and a lot older. There’s only one that I would care if the CEL came on, and one that I worry about only on the rare occasions when it turns off for a few minutes. I have two cars where the CEL is always on due to a vehicle speed sensor. Has no effect on operation and would cost more to fix than I paid for the car. The only downside is that it might mask some other code, but unless the CEL starts flashing there’s little chance of anything serious. For a $300 car with 200,000 miles, I can put up with a teeny amber light.

Those things would be more useful if they could detect real problems like combustion leaks or transmission slipping.

fyi, that could cause symptoms depending in which mode it fails, such as making it difficult to fill the gas tank w/out the pump repeatedly turning off.

Some of them are important. There are codes that speak about engine timing and transmission performance.
If the light has “been on” for twenty years how would you know if there are any “important codes” begin the “unimportant ones”.

Purge valve (on my truck) is on the intake. It had failed open. I couldn’t really tell any symptoms other than the gross evap leak code and the “tighten gas cap” message that would occasionally flash on the odometer display. But, I replaced the valve, no light since.

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If the light’s been on for twenty years (it has, in one case) and the engine runs well, I’m not going to rock the boat.

Unfortunately in New York we can’t do that. Check engine light on, no state inspection

… and NY is far from being the only state that tries to control vehicle-generated air pollution by checking emissions at the inspection station, and where the presence of a glowing CEL automatically turns you away from the inspection station.

Speaking as someone who maintains his car meticulously–and who resents others who don’t–I am very glad that NJ, NY, and several other states are as strict as they are in regard to emissions.


I think I may have said this before but some states i my opinion [ I don’t know what states they are ] but I do know that if you spend a certain amount and it still don’t pass they give you a waiver to pass till the next time then the owner does not have the money for needed safety repairs like brakes tires etc I would rather see a car on the road with a CEL on than bad brakes or bald tires or whatever else might be wrong.


I agree. I’m looking back and I think I used the term “unfortunately” incorrectly. Apologies. I do believe that any vehicle should be reviewed for emissions and safety by a qualified automobile mechanic at least once a year.

It has been mentioned a dozen times that to determine if the faults have been erased to review the emission monitor data but I didn’t see where that had been acknowledged.

Commonly there are three types of fault codes; current, pending and history. History faults will drop off after a certain number of ignition cycles and will not cause a failed emissions inspection.

Now to further confuse the OP, late model vehicles can have a “Permanent” fault in the system. A permanent fault is not truly permanent however it can not be erased by a technician. A permanent fault will be deleted from the memory after the PCM has verified the problem no longer exists.

The example below occurred while I had the fuel tank removed from the vehicle, the PCM could not read the fuel tank pressure sensor.

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