> Does the check engine light error code need to be explicitly erased after fixing a problem for the light to go off?

Does the check engine light error code need to be explicitly erased after fixing a problem for the light to go off?

Posted at: 2015-01-07 
Many of the error codes do in fact need to be cleared before the check engine light will turn off, but it's not a difficult thing to do. If the seller thinks all it needs is clearing, then ask him to clear it. If the problem is still present, it may take up to three "drive cycles" for the light to come back on. After the light is cleared, take it for a test drive. During the test drive, drive it for a few minutes then shut it down for a few minutes, and repeat the cycle until you've driven and shut down at least three times. If the light comes back on there is another problem that he hasn't fixed.

Of course, you're not exactly buying a new or pristine automobile here. Maybe you shouldn't be too worried about a check-engine light. A vehicle this old is going to have some mechanical issues.

The seller could clear the code but the problem may present again within a couple of days of driving - it would also be nice to know what the code is before it is cleared - guy sounds sketchy and is asking way too much for an engine that looks like that- are sure it hasn't been in a flood or a fire?

Shady, yes the code has to be cleared and is the step after replacement. Should be done before calling it ready for sale.

A complete drive cycle will take time and gas. a few complete drive cycles will take three times as much.

You could just get the code read now and see if there are codes for those ignitor coils still stored.

This car is one of the most complained about on answers in my estimation.

Be careful, make him prove why he has not completed all the work.

Getting a car from the Ford dealer may be smarter. and getting warranty coverage sponsored by ford is smarter.

If the car is too old for that, then you proceed with caution and buyer beware.

Get a full inspection by ford and ask for the future known needs to see if you want the POS, and to know what is going to be on your to do list.

Then negotiate a fair price, already, you need to allow for the ignitor coil or coils which have not yet failed but are likely to be your next rodeo.

I call BS (business sense) on this seller. If you're in love with the outside, take it to an auto parts store and get the OBD codes read. They will tell you what the code is and what it might take to fix it. I would make a counter offer (again, only if I really loved everything else and couldn't find another deal like this anywhere) minus the value of your time to figure out the problem and what it will cost to fix it. Is that a picture of the engine? It looks like a wrecker. It's all rusty and dusty. The seller couldn't be serious about KBB full value. I've had cars that were over 200K miles and didn't look that bad.

In most states it's against the law for a car dealer to sell a car with a check engine light.

A real mechanic would never sell a vehicle that has a CEL lit. They would also have at least a cheap OBD II code reader that can erase codes! You're going to get screwed by an idiot!

The code clears by itself after the engine has completed a drive cycle (see post below on drive cycles). But hear this: RUN from this vehicle. Clearing a code takes all of 2-mins with a scan tool. The fact that he didn't clear the code means that he threw two coils at it and they didn't fix the problem. Read the Rule #1 on the second post below to understand that.

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Everything else looks good? I'd back off the deal just by the looks of that engine bay.

Sounds sketchy, but what he's saying is true. It's just a little CEL scanner you plug in under the dash to erase codes, I have one myself. If he's a mechanic he should have one too and be able to do it. Sounds pretty dicey.

The fault needs to be erased, it does not go off on it's own. Get the owner to erase the fault BEFORE you buy it and then take it on a test drive to make sure everything is how it should be.

I was checking a 2004 Ford Focus to buy. The check engine light was on. The person selling it was a mechanic. he tried to explain to me what was wrong but I had trouble understanding because his english wasn't too good.

He pointed at the ignition coil/spark plugs assembly and said that 2 of them were bad and were replaced.

when i asked him why the check engine light is still on if the problem is fixed, he said that the "error code has not been erased", and that he only needs to plug it to a computer and erase the code.

can someone please help validate that statement? Doesn't the check engine light automatically go off when the issue is fixed? does it have to be explicitly turned off by erasing error codes?

i've attached an image with circles around why he said were replaced.

Its a 2004 Ford Focus SE with 137K miles on it. everything else looks pretty good on it. he's asking for $2900 (KBB price is also 2900) but If the check engine light is on, is it worth buying for that much? if not how much should I spend on it?

Usually needs to be cleared. If you don't have a scanner with that option, you can try unhooking the battery for a minute.

po301 and a po304, those codes should not really be an issue but they will be stored for 40 drive cycles unless you have it reset. if you are in an area that does a smog check, that alone can create an issue,

No scan tool will clear the code, you have to fix the problem first, then and only then the CEL will turn off.