Question about 2001 Toyota Corolla

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


I have another problem on my 2001 toyota corolla and I was wondering if you could help me. I refuse to bring the car to the dealership since I know for a fact I will get screwed! Like I stated in the last thread, everything has been replaced as far as the exhaust system goes. I still have the check engine light with a P0420 code for bank 1 and 2 and I do appreciate the advice you gave me on that. I noticed 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 on the check engine light, that code went away, which I thought it was fine. I cleared the code 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 your opinion since I respect someone like you and not the crooks at a Toyota dealership that are only in it to make a buck. 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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  • jackie jones Dec 11, 2008

    I have replaced both oxygen sensors, cat converter(toyota part) maf sensor, spark plugs, ...I even passed emissions! Why is this damned light still coming on??!!!

  • mdmarasim Dec 18, 2008

    I have a 2001 corolla with 107K. Transmission fluid looks good but i am skeptical. It changes fine and no problem. I bought it used. I dont know whether the previous owner changed it or not. I have heard horror stories of cars getting messed up once they change it.What is your suggestion regarding this changing of transmission oil at 107K.



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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.

Posted on Sep 29, 2008

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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


Well I got the 02 sensor from Rock Auto. It is a bosch, but maybe it was an aftermarket one. Do you have a brand you recommend???

Posted on Sep 29, 2008

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Toyota Corolla Code P0171 Check Engine light

Code P0171 on Toyota Corolla Q: What could cause the code P0171 on 2002 Toyota Corolla? A: The code P0171 reads "System Too Lean (Bank 1)". This means that the air-fuel mixture coming in to the engine is too lean, or there is too much air and too little fuel. This could be caused by a number of reasons, such as bad airflow sensor, vacuum leaks, low fuel pressure, clogged fuel injectors, etc. To know exactly what caused the problem, your mechanic can do a few tests.
From my experience, the airflow sensor problems are fairly common; sometimes the sensor just gets dirty and gives false air flow readings causing lean condition. Again, your mechanic can test it.
If the airflow sensor is causing the lean condition, it will need to be replaced. If the sensor is just dirty, your mechanic may suggest to clean it (cleaning the airflow sensor is very delicate procedure) as a temporary solution - sometimes this could work.

on Dec 07, 2009 | Toyota Corolla Cars & Trucks

2 Answers

Engine light code p171 comes up. I recently changed the air flow sensor. Everything else is working fine. What can this be in a Toyota Corolla 2003?

DTC P0171 is set when fuel trim is driven rich beyond a certain value. Possible causes are:
1. Exhaust system leak.
2. Improper fuel pressure.
3. Fuel injector restricted.
4. Defective heated oxygen sensor No. 1.
5. Defective Manifold Absolute Pressure (MAP) sensor.
6. Defective Engine Coolant Temperature (ECT) sensor.

System Too Lean. This code will set when an air fuel ratio sensor (O2 sensor) gets lazy.

Also, check for a vacuum leak on that side.

Jan 26, 2011 | 2003 Toyota Corolla

1 Answer

My 2001 toy,corolla showed a code of po171 so i changed the oxygen sensor then showed po300 , the car hesitate on excelleration but if you back up a little on the throttle it runs fine like the cat is...

P0171 is a lean code. Most common cause for this is a vacuum leak. The cat would throw a P0420 code. Don't mess with the cat. The P0300 code is a random misfire code. Look for a vacuum leak first.

Sep 24, 2010 | 2001 Toyota Corolla

1 Answer

2006 Toyota Corolla Code P0171 What could be the problem?

po171 means the air fuel ratio is lean (not enough fuel) so you must check for anything that can do that a good example would be a vacuum leak that allows non metered air to enter the engine (more air same amount of fuel = lean mixture) or a clogged injector (same amount of air less fuel = lean mixture as well)

Jan 06, 2010 | 2003 Toyota Corolla

1 Answer

I have a 2001 toyota corolla and I am wondering if theres any other make of toyta vechile that would match mass air flow sensors with a corolla. If so will they work the same? Please help

A Chevrolet Prizm is the same Toyota Corolla car. Scion is Toyota also. All the mass air flow sensor of the same year and same engine size should be the same.

Oct 07, 2009 | 2001 Toyota Corolla

1 Answer

2000 Toyota Corolla P0171

When the fuel trim is high teens or in the 20s then its the MAF that the problem. If fuel trim is normal, 2-5 then its the O2 sensor.

Buy "Electrickleen" at the parts store.
Remove the MAF sensor, WHILE COLD, and blast the wire inside with cleaner.
The "hotwire" gets gummed up and changes the resistance of the wire so you get a bad input to the ecu and it trys to lean out for a rich condition that doesnt exsist.When it cant adjust anymore it trips the po171 code.

Jun 01, 2009 | 2001 Toyota Corolla

1 Answer

Check engine light code P0171 activated on my 2001 toyota corolla

p0171 is lean condition bank one. you could have a vacuum leak a bad map sensor bad maf sensor clogged fuel filter low fuel pressure. start with the vacuum leak first.

May 05, 2009 | 2001 Toyota Corolla

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2001 Toyota Corolla Malfunction Indicator Light

go to the autoparts store and they will pull the check engine light code then send me a message and i will look the code up explain it and tell you how to fix it. good luck and the autoparts store will do that for free, take care and let us know

EZ Automotive/U.S. Army

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