Question about 2001 Toyota Corolla

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Check engine light on a 2001 Toyota Corolla

I have more problems on my 2001 toyota corolla and I was wondering if someone could help me. I refuse to bring the car to the dealership since I know for a fact I will get screwed and let me tell you, I have in the past one to many times! Everything has been replaced as far as the exhaust system goes (converter, 02 sensors, pipes, muffler). I still have the check engine light with a P0420 code for bank 1 and 2. This came back on about 3 weeks later. I noticed about 3 days ago that the car is hesitating when I am at a stoplight once in a while or after I start accelerating after I have been at a stop light. The car is starting fine and my gas mileage is fine. I have a new code that is a P0171 code which states the system is too lean. I have read that it's the MAF and that it should be cleaned. My boyfriend cleaned it last night with electronic cleaner. When he put it back in the car and I started the car and checked the codes with the OBDII sensor, that code went away, which I thought it was fine. I cleared the codes last night and I drove it a little today around the neighborhood to test it and the same thing is happening as far as the hesitation goes. The check engine light has not come back on yet. I have ordered a new MAF since I think it is faulty, but I would like someone's opinion on this. I want to add that the last 02 sensor that was replaced was the one before the converter closer to the engine and a body shop did this. Ever since they replaced that one, I noticed it was harder to accelerate and then I started getting the hesitation about a few weeks later and then the P0171 code came on. I am thinking of replacing the MAF and also maybe replacing that 02 sensor since it may have been faulty. Sorry I am rambling. Thanks. Any advice is appreciated. Thank you so much.

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  • Marvin
    Marvin May 11, 2010

    I would clean the MAF and replace the O2 sensor.



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I have had numerous problems with my 01 Corolla. Yikes! You need to understand that Toyota will not submitt to universal parts. You must use their parts. Especially on the Cat Converter. Further, don't EVER go to Meineke for repairs if you haven't already. I use to get my authentic parts. They are truly the bomb on pricing.

I had the p171 and p420 codes. I replaced the mass air flow sensor, cat converter, and put on new iridium spark plugs.

Posted on Nov 19, 2008

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No need to replace the MAF. If it was bad, the check engine light would have come right back on as soon as you started the engine. The MAF not only measures the air going into the engine, but also measures the air temperature. Those 2 circuits are constantly sending info the the ECU. If either would fail, the ECU would light the check engine light. P0171 is a common code for incorrect readings (dirty) in the MAF. Cleaning it always helps, and cuts off the light. Your acceleration problem may be either a wrong Air-Fuel sensor (the one before the cat), or an "aftermarket" AF sensor. "Aftermarket" AF sensors have been shown to not work properly in Toyota vehicles. Hope this helps

Posted on Sep 29, 2008


THANK YOU!!!!!!!!!!!!!

Posted on Sep 29, 2008

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Posted on Jan 02, 2017


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SOURCE: Another problem on my 2001 Toyota Corolla - P0171 system too lean

yes i would replace the front o2 as it is the one that controls fuel maps especially if your getting the low voltage, i would replace with o.e.m., the dealership not the autozone knockoff, but you can install it easily and dont go paying anyone if you have one of those handy boyfriends in your toolbox ; ). i would do that and if its been a while throw some new plugs and wires on there to. should fix it up, i wouldnt worry about the maf. sorry for being so late with this reply, ive been sick this last week and sleeping alot i appologize and promise to answer your questions sooner next time, once again sorry, and take care, make sure to keep me informed about whats going on with your car.

Posted on Oct 06, 2008


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SOURCE: I keep getting code p0420. I replaced 2 cats, all

P0420 code is usually a sign of s weak fuel pump, and needs to be replaced. Also if you replace the pump and still get that code, check your fuel lines back by the tank and make sure that they are not pinched or smashed. this will also give the same code due to restricted fuel pressure, on the ruturn or supply line........ Good Luck

Posted on Oct 08, 2010

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Another problem on my 2001 Toyota Corolla - P0171 system too lean

If you had a bad MAF, the check engine light would have come on instantly. Replacing the MAF will NOT cure your issue. P-0171 is a common code, and cleaning it always eliminates the P-0171. Regarding the sensor, there are 2 different ones, and they do NOT interchange. If your body shop put in an "aftermarket" air-fuel sensor (the one closest to the engine), you can expect hesitation issues.

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