2004 2.7L Prerunner CEL on and off?

Hello everyone I'm here because I seem to have some problem that I cannot find. I have a 04 Toyota Prerunner 2.7L. The only aftermarket things that it has is basically an exhaust and an air intake system(if this means anything). For about a year now I have been trying to figure out why my trucks check engine light comes on and off. It comes on for a few days and then goes away on its own. I have gone through and looked underneath the truck and I don't see any leaks or anything broken. The truck itself runs perfectly which makes me wonder if it is possible that it's some sort of sensor? One thing that I will be testing here today or tomorrow is my fuel tank cap. I purchased one with a lock and it may be that for some reason? If anyone has any thoughts or have had the same thing let me know! It doesn't worry me it just bugs me that the light is on and off.

Thanks in advanced guys!

 

Take it to Autozone, and have them read the OBD error code that is stored in the computer. Then get back to us.

 

Alright UPDATE: So I took a trip down to the Autozone here and I got the check engine light checked. There were four codes that came up, well technically two codes because they were repeated. The codes were P0442, P0446, P0442, P0446. The "tech" there printed off what those codes were: P0442 EVAP System Small Leak(0.040") and P0446 Evaporative Emission Control System Vent Control Circuit.
The two recommended parts were a Fuel Cap $10.99 and a Canister Purge Valve $61.99. I didn't purchase either since I have my original OEM fuel cap. I replaced my fuel cap for now to test that. I will post a picture of my both fuel caps. The one with the lock is the one that I had been using until today when I switched back to the OEM. If it does turn out to be the gas cap, are there any options with a lock that you would recommend? I still would like to get a lock on it for "safety" reasons (don't want some jelly person putting stuff in my truck).

Thanks again.

 

Whenever you make a change in order to clear a CEL, you should clear the codes. Then, if the repair did not work, the ECM will re-set the code. You should get a code reader/clearer so you don't have to go down to Autozone every few days.

 

So I changed the gas cap and got the code reset, its been almost a month now and the light never came back.

 

1 issue. when you clear your fault codes, the computer resets everything. including the emission readiness monitors. this means that you have to go through a full emission check list of tests before the computer will throw out codes involving anything on that checklist. and a leak from a gas cap is one of them.

sorry bud. you shouldn't have reset your computer since it will take much longer to go through these cycles than it would to just let the system retest for the gas cap.

 

if you do end up needing to perform the monitor tests. here's the instructions on how to do it.

 

Well to this day there is no CEL so I will keep an eye on it. If it ever does come back I will for sure come back and let you guys know. Im positive that it was the cap because there was nothing wrong with it when I replaced it in the first place it was just because I wanted a lock on it. But thanks! I appreciate the time you took to let me know this info!