[FIXED] 2001 Toyota Corolla p0171 system too lean

Hey guys I'm new at this forum but been a member for a year wanna star by saying my English is really bad and I will try my best to explain my problem and also by thanking Paul danner for making this nice repair videos that's had help me a lot thanks man keep up the good work.. ok so I have a 2001 Toyota Corolla with a code p0171 system too lean I stared by putting the smog machine to the intake to find any leaks founded a exanaut manifold donout before the catalytic conver was leaking real bad and I toght that might of fiz the issue customer took the car to another shop and they sold him the air fuel sensor and the mass air flow meter and they did replace them because they look new. Today I drove the car for about 20 miles and code came back on same code but this time also p0420 catalytic efficiency below i did a check up on the cat. And it looks like the other shop open up 2" holes one at the front and one at the rear now my question is would a bad catalytic give you a lean condition? After I check that I wanted to make sure there was no other leaks after smog test found nothing my fuel trims Long fuel term is between 17.2 and 20.1 shot fuel trim is between negative -10.8 and -11.0 now I'm trying to get better at this fuel trims numbers. Also check my 02 sensors and my uptreem sensor seems to be switch just fine also check the purge solenoid don't know what else to check for. Thanks guys.

I have seen a few of these Corollas with fuel injector issues causing lean conditions. ScannerDanner has a few videos showing how to do an injector balance test on these. If everything you have checked so far looks good, I would try to do a balance test next. But, your short term trims seem to be countering your long terms for a total correction of about 10 which isn't too bad for an old car. That's not enough to trigger a light, which brings me back to the freeze frame data. It is crucial to know when the code is being flagged so you can re-create the conditions and find your culprit. Happy hunting!

It would help a lot to know the fuel trims at both idle speed and at 2000 to 3000 RPM.
I would also help to get an idea of what B1S1 and B1S2 output is like at the same RPM's.

josueivanruiz wrote: I have seen a few of these Corollas with fuel injector issues causing lean conditions. ScannerDanner has a few videos showing how to do an injector balance test on these. Happy hunting!

These ones?

thank you guys for the help.. OK so last night i stayed awake until 2am watching scannerdanner videos related to fuel trims i know sounds crazy but had to because i had this car for 3 days already and customer need it. anyways so i came today to work and i plug in my scanner since the long fuel term was at max 25% i read on Mitchell that was a good number so i took the change and changed the CATALYTIC since i had code p0420 i had one here at the shop in stock after installation i turn on the car and waited for close loop, i noticed that my short fuel trim was not at the -11.00 and -14 it actually changed to positive number close to 0 moving up and down took the car for a test drive clear memory codes i drove the car for 85 miles check engine use to turn on at 20 drive so came back check for any code no pending coded no history code and no active coded were set so took the car to the smog station pass like a champion customer will pick up his car tomorrow... so the cat was the hold issue never seen a cat gave you a p0171 code.. thanks guys hope this helps.. and sorry for the spelling

victor1979 wrote: thank you guys for the help.. OK so last night i stayed awake until 2am watching scannerdanner videos related to fuel trims i know sounds crazy

Been there... :side:

victor1979 wrote: so the cat was the hold issue never seen a cat gave you a p0171 code...

Me neither! :blink: This is probably the last part I would have changed based on the code. Did you happen to change either of the oxygen sensors at the same time?

Not that it matters, it's fixed! Congratulations, sir.

Tyler wrote:

victor1979 wrote: so the cat was the hold issue never seen a cat gave you a p0171 code...

Me neither! :blink: This is probably the last part I would have changed based on the code. Did you happen to change either of the oxygen sensors at the same time?

Not that it matters, it's fixed! Congratulations, sir.

Yup, can't argue with results!