check engine light on for 2001 corolla

I have a 2001 corolla with 37K mi on it. The check engine light came on today. took it to advance auto parts to read the code. It showed P0171 ( System too Lean ) and P0300 (Random Misfire). Called up a toyota dealer and the technician think it might be bad gas. I buy gas at name brand gas stations and sometimes from BJs. I am not sure if the problem is with gas. I also been up to date with maintainence.

any idea what the problem might be ? any help is greatly appreciated.

thanks
Jay

Do you feel any loss of power? any different at all before the light came on? random misfire usually give the hesitate, if everything just feel fine then probably just the gas cap is not tight enough, since you mentions that you have been up to date with the maintainance why dont you unplug the EFI fuse in the fuse box for 20 sec,then put it back, it should clear the check engine code and if it check engine light comes on again in a few minutes or miles there must be something else that causing the problem. If it is not then the gas cap is the problem.

There doesn't seem to be any loss of power. the car doesn't feel any different than it was before the light came on. Its been 4/5 days since the gas was filled up. Can the light come up after so many days ?
anyway I reset the check light using the EFI fuse. All I can do now is wait to see if it happens again.
thanks
Jay

The code will almost definatly come up later. Its back up stored in the ECU in a redundant memory. Plus, I wouldnt reccommend pulling the EFI fuse, because that will not reset your computer.

To reset your computer, you will need to get it cleared by someone with a code scanner, and a good one, not a cheap ass one from Autozone or whatever. OBDII saves it, trust me, and it will pop up.

Also, you can get a scanner, and a good one will tell you what was happening at that time with the car, under what conditions. And if something is not right, you can identify it, and deal with it. Just clearing the codes for the MIL or whatever you want to do is rediculously stupid.

Lean fuel and occasional misfire could be nothing. But you know, I can bet there are a dozen different reasons that these things would happen. And if there is still a problem with your car, and you ignore it and clear a light, then something that could have cost you a few hundred bucks could come back and bite you in the ass. Ignore it, and you very well could have to get a new engine or a new car.

Oh, one more thing; Telling someone to just pull a damned fuse is bullshit. Giving them possiblities of whats wrong, or something else helpful would be better. YOu claim in your profile to be a Master Mechanic. In my opinion, your fuse suggestion isnt very masterful at all. Im not going to claim to be anything other than a mater debater, but you know as well as I do that there are checks and methods to elimiate causes of his MIL

Oh, and by the way, shitty mechanics fix what is broken; Excellent mechanics fix the CAUSE of why something is broken. Big difference.

Something to consider, just nothing personal.

This forums is open for everyone, I joined this forums to share with everyone who is willing to learn and discuss their problems or sharing their experiences. I took everybody opinion and really appreciated no matter it would solve problems or not and thankfull enough how someone took the time to read and respond back to this forums.

If any one who is mechanic up there will know, how hard it is just to read and think what might be a real problem, because just to listen to the people that have problems with their car without really see for themselves is not easy, all I can do is to try to help with my own experiences, if it does not work than go to another step. If you read my respond on the top for jay97rodeo, I clearly stated that if the light comes on again that could be another reason.

Wissnx01 is right that you need to have OBDII the good one to read and to clear the code but that means he has to spend another top dollar just for the scanner, I believe that he is here to look for the answer that could be for free or something that he could learn.

There is nothing wrong to pull EFI Fuse if he has a gas cap problem, like i stated earlier, if he has another problem the ECU will respond back again then the light will comes back on.

Wissnxo1, Thank you for your opinion. By theway I am Master Mechanic and is ok if you don't like my answer for jay97rodeo. I already made it clear to him that if the caps is not the problem the light will go back on.

I know its hard, but I must have read, and Im not shitting you, 100 threads where poeple were told to remove fuses. Over have of those threads continued because there was still a problem,and in one case, someones engine destroyed itself.

Im not flaming you, I want trying to, but sometimes, as you know, free or inexpensiver repairs are a myth. Sometimes you have to bend over and take it.

Any new information on this topic since I've got the same problem and haven't taken it to a dealer yet.

jay97rodeo has not post any more info since then, hope it solved his problem.

ncborn67, if you have the check engine light on, please have it read the code first.

I did and I got P0171 System Too Lean Bank 1

Try to clean the throttle body (where the air intake goes to), with carburator cleaner, you can get this at autozone/pepboys. Also check the air filter, replace it if its dirty, check fuel cap is tight. How many miles is your car Ncborn67? the reason I asked, if you have IAC valve problems you could take this to dealer to get replacement if it still under warranty. Sometimes bad gas, fuel cap not tight enough, dirty filter will make the CEL to go on.

I got different diagnosis - maybe bad spark plugs and wires , maybe bad gas or maybe something else. I got the feeling the mechanics were just planning to replace parts till the problem went away.
anyway the check light hasn't come back yet. I had checked the air filter coz I read somewhere about dirty air filter causing the MAS sensor to clog up and cause the check light. the air filter was clean. the spark plugs were not replaced at the 30K service coz they are iridium or platinum or something and should last 60K. I have one more mechanic ( not a dealer) whom I need to take car to. His place is a bit far. I was trying to avoid driving that far..

I just purchased the car 2 weeks ago today.
It just a little over 30,000 miles on it when I bought it. It now has 31,000 miles on it.
I also went to Auto Zone and had them test it. I got the one error.
I filled up with gas and put the cap back on and made sure it was tight.
The light came back on a day later.
Thanks ishop4less for your suggestions. I will try it.
I didn't purchase the extended warranty so I sure hope whatever is wrong with it isn't anything major!
Thank you all for your replies.

Whatever you do, dont let someone tell you to pull the stupid EFI or ECU fuse, that will just be a problem later. If you dont know what your doing, take it somewhere, otherwise your going to have a car with 31,000 miles forever.

okie dokie

Has anyone realized who is this man name "wissnx01" ? What is his problem? the ishop4less try to help others but look what he got in return from wissnx01 :

wissnx01 qoute:

{" Oh, one more thing; Telling someone to just pull a damned fuse is bullshit. Giving them possiblities of whats wrong, or something else helpful would be better. YOu claim in your profile to be a Master Mechanic. In my opinion, your fuse suggestion isnt very masterful at all. Im not going to claim to be anything other than a mater debater, but you know as well as I do that there are checks and methods to elimiate causes of his MIL}

Ladies / Gentlemen Thank God that wissnx01 has been banned, but too bad that he is back at wissnx-01 now, if he banned again maybe he will use /01 or +01 after the wissnx, who knows what he is going to use. Guys you should browse and see other post that he left....dude just terrible. This forums is suppose for people who need help and people who willing to help, We don't need people like wissnx01 or 02 or 03 who knows what he is going to name himself.

I have ASE certified, and what ishop4less said is right, NOTHING WRONG TO PULL EFI FUSE TO CLEAR THE CODE, IF IT STILL HAVE PROBLEM ECU WILL RESPOND BACK THE CODE. That is absolutely correct.

P0171 most problems that I knew is MAF sensor dirty/faulty. A dirty MAF sensor can cause a check engine light. The cleaning procedure is simple and inexpensive. Those owners who have installed a re-usable air filter (such as the TRD unit) will likely need this service sooner than others, since a small amount of the oil used on these filters is sucked in the intake tube and tends to coat the MAF sensor.

For all models, the MAF sensor is located just after the air filter housing. A full size pair of pliers will be helpful in depressing the lock on the electrical connector, just remember it's plastic, only squeeze enough to disengage it. Due to the layout of the components on various models, a 90 degree screwdriver may be required to remove the screws holding the sensor in the intake tube. Once the sensor is out, use electronic cleaner to spray the dirt off of the fine thermistor wires inside the unit. If you are going to use the little plastic tube provided with the cleaner, do not stick it down inside the sensor. The wires are very delicate and this is a very expensive sensor to replace. Once clean, let it dry, re-install it, and re-attach the electrical connector so that it locks into place. No other computer or electrical considerations are necessary, either before or after the service.

Guys, I am also seeing the same problem. Initially, it appeared when i heard knocking engine sound yesterday. Then i immediately checked the engine oil, It was way below the lower mark. I will have to take it to a mechanic to find out the cause of oil leakage or burning. But, today i put the oil and had the level in between the markers on dip stick. After starting the engine, i am still seeing the Engine Light. Although i didn't hear any knocking noise like the other day, i am still suspecting something is wrong. Is it possible that, the Engine light was not lit when the oil level was low for sometime and since i was running at that level, the engine is badly screwedup. Because i don't seem to see the warning light few days back. OR is it possible that since i filled the oil half way between the marks, the Engine Light is still on. I am a novice, so please bear with me for all stupid questions i may be asking. Anyway, i am going to take the car to the mechanic (Jiffy Lube) and have it checked. I will also get the oil and filter change done, as i have driven 6000 miles since my last change. Also, is a mechanic like JiffyLube is OK to deal with the Engine Light problems or should i have to go to any particular mechanic who is an expert in these. I would appreciate your replies to my queries. thanks.

Thank you all very much for all the information. :)

I just got back from autozone ... and my CEL was on .... they told me I had 4 misfiring cylenders ... and the system to lean bank 1 ... I had recently installed a cold air intake and thats then my CEL went on... Im taking it to Project Import ...on Sat to see if they can help... I think most corollas have this problem ... dunno why

very easy video instructions step by step http://youtu.be/Aidr-rl54Ps?list=UUJep1PJGA7xPXGMr3lG1aXw