Corolla Check Engine light - Toyota Nation Forum : Toyota Car and Truck Forums

johnsmith2004 · 10-11-2007, 12:58 AM

2000 Corolla CE 75000 miles. The check engine light has been on for almost few months. I tried to use fuel cleaning fluid, but not working. We went to Autozone and the code was P0171 bank1.

I have the code and freeze frame data printed out.

engine spreed 2603 rpm
load value 41.1%
coolant temp 185 F
intake air temp 96F
short term fuel trim 3.9%
long term fuel trim 31.2%
long term fuel trim3 -100.6%
short term fuel trim3 -100.6%

I heard someone said If the Long term fuel trim number is high (over 10).
Then you need a Mass air flow sensor. Is that true? Can I just replace the Mass air flow sensor or also oxygen sensor? Thanks for comments.

johnsmith2004 · 10-12-2007, 09:39 AM

Anyone can help me? thanks a lot.

buckerboo · 10-12-2007, 09:50 AM

Cheapest and simplest thing to try first is to remove the mass air flow sensor, clean it, reinstall it then reset the system. If the light returns with the same code then I would replace the A/F sensor (o2 sensor) bank one. I have not had to replace many MAF sensors, if any. Usually a cleaning of it will work. Worth a try, it is free.

mikered30 · 10-12-2007, 02:01 PM

^^ Do what he said. CRC makes a MAF cleaner that you can buy at any parts store. Make sure not to touch the filament on the MAF sensor.

johnsmith2004 · 10-12-2007, 02:29 PM

thanks for comment. I will buy the CRC cleaner. How can I clean MAF sensor? By unscrew two bolts, clean insides.

mikered30 · 10-12-2007, 08:06 PM

Quote:

Originally Posted by johnsmith2004

thanks for comment. I will buy the CRC cleaner. How can I clean MAF sensor? By unscrew two bolts, clean insides.

Try this. http://matrixowners.com/forums/page-1-t27838-s0.html

c101380 · 10-30-2007, 03:39 PM

I have received the same P0171 code, which is supposed to be for the pre-catalytic converter O2 sensor. I have already pulled out the sensor (which has no corrosion and is showing the correct resistance) but for some reason is still causing the check engine light to come on and give me the same code. I don't know what to do because my O2 sensor appears to be working correctly and I have already cleaned the MAF sensor, changed the gas cap and run fuel injector cleaner through it . Is there anything else that could cause this code ?

johnsmith2004 · 11-26-2007, 12:46 PM

It seems even though people clean the sensors MAF and O2 cannot solve the problem yet. I just heard someone mentione we can clean the oil tank to solve this problem. But, I check the toyota manual, it said the gas tank does not need to be cleaned in the new version of corolla. Anyone can help us how to solve this problem......???