Check Engine Light Goes Off After a Week+

[2mrchio]

Is there any instance where the Check Engine Light will come on, then go off a few days later? In my case the light came on, and about a week or so later, just when I was set to purchase a code reader to research it, the light went out. My wife uses it as a daily driver, but she said that there wasn't anything out of the ordinary going on.

The only one that I can think of is the gas cap. She fills it, so I can't say if that was the problem. I even checked it while the light was on.

 

[Robert]

Yes some of the diagnostics tests that are ran after a cold start will do that if the problem is corrected. The code should still be in memory though. The gas cap is probably one such code. I would go to Autozone and have them read the "trouble" and the "pending" codes to see if anything comes up. If it turns out to be a P0455 then it was in all likelyhood the gas cap. After 40 successful drive cycles without seeing the error again, the code will be erased from memory. If the CEL is off, then right now it isn't seeing the error while driving.

 

[Opera House]

My 97 had a 422

Small evaporative leak that went away for three weeks and came back. It was the vent solenoid under the spare tire. It was stuck open and should have been a large leak. But, the filter screen on the valve was so clogged that it only tested small. The solenoid rusted to pieces evidently because the tire throws up mud and water. You can see it through the tire well just over the axel. Thinking this will be showing up on a lot more Explorers. Depending on the type of driving, the evaporative test may not be performed every time you drive.

 

[KillerXLT]

It could be your 02 sensors. I just had the same problem except mine comes on and off after long trips. I work at a dealership and had one of the techs check out the code. It comes up as the 02 sensor. The problem is that it does not specify which one. I was tolds there are 2 each cost 87.00 . Hope that helps you out.

 

[phat97exp]

I was told there are 3 or 4 sensors on my explorer, im stil confused on how many there are? If anyone knows for sure thad be great to know.

 

[2mrchio]

Originally posted by KillerXLT
It could be your 02 sensors. I just had the same problem except mine comes on and off after long trips. I work at a dealership and had one of the techs check out the code. It comes up as the 02 sensor. The problem is that it does not specify which one. I was tolds there are 2 each cost 87.00 . Hope that helps you out.

Thanks for the update. And thanks Robert for clearing up when and if a CEL will reset itself. It makes sense that if certain readings return to normal, the light should go off; I was mistakenly under the impression that it stayed on until it was cleared, either through reader reset or battery disconnect. I will proceed to get the stored codes read, and report them back here.

 

[2mrchio]

Originally posted by phat97exp
I was told there are 3 or 4 sensors on my explorer, im stil confused on how many there are? If anyone knows for sure thad be great to know.

The SOHC has two pre-cat sensors and one post-cat sensor.

 

[Robert]

The SOHC and the V8 have 4 O2 sensors (not 3). One between each exhaust manifold and catalytic converter. And one between each catalytic converter and the muffler. The OHV from '96 up has 3 O2 sensors, one each beteen the exhaust manifold and the 'Y' pipe and one after the last catalytic converter and the muffler.

 

[2mrchio]

I realize that it doesn't make it correct, but I based my answer on a diagram emailed to me from Torrie @ Ford Parts Network. I'd post it, but it is larger than 640x480.

I have since heard back from him saying that the OHV has 3, the SOHC and V8 have 4.