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Corolla 2006 And Ongoing P0171 Code

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Well, I am finally at my wits end. My 280,000 plus mile corolla 2006 has the p0171 CEL code. the car is in good condition. I change the oil regularly and rotate my tires (a deer did hit the passenger side fender in '08).

I have tried everything to solve p0171 problem. I have had the problem off and on since 2011. At first I would just disconnect the negative battery terminal to clear the code. However in April 2013, I made a concerted effort to solve problem. Below is the general chronological steps I have followed to solve problem.

1. installed new air filter

2. installed new fuel cap

3. cleaned MAF with CRC electrical cleaner

3. installed refur Cordone MAF (Autozone)

4. installed intake manifold gasket - Felpro (black)

5. installed intake manifold gasket - Toyota (orange) got rid of Felpro

6. replaced spark plugs with NGK 5464 and purchased new fuel cap

p0171 code went away until end of July 2013, then it came back ...

1. installed new NGK 5464 spark plugs.

po171 code went away until 828 miles, then it came back ...

1. cleaned orange intake manifold gasket

2. replaced refur Cordone MAF with another refur Cordone MAF (still in warranty)

3. replaced throttle body gasket

4. finally ... replaced upstream O2 sensor ...

I am bald so I can not pull my hair out. Thanks for any advise.


It's likely a small vacuum leak. Check all vacuum hoses, brake booster hose, and PCV hoses for leaks from cracking or hardening and lack of proper seal on fittings... If it wants to stall when pumping the brakes hard when idling, it could possibly be a leaking brake booster.


Thanks DOM and CorollaMike ... sorry for not responding sooner (had stomach virus).

DOM, I thought I checked for vacuum leaks using carb cleaner then throttle body cleaner several times. I did replace pvc valve then checked for leak. did not check brake booster hose. where is that located? also, what do you mean by "lack of proper seal on fittings"? I will check pumping brake test for the brake booster.

CorollaMike, great site. lots of stuff. will have to walk through each once I look at the vacuum leaks and brake booster test.


Brake booster is below brake master cylinder and brake fluid reservoir. A vacuum hose goes from it to intake manifold, just behind throttle body... Check all vavuum hoses and PCV hoses, and make sure they good and tight on their fittings at both ends of the hoses.

Brake booster hose fitting on intake manifold is hidden once throttle body is reinstalled and may be overlooked, as shown in center of photo:


Thx DOM ... I understand now. This was a tricky hose, but I am sure I replaced properly. However, I am not happy with some of the fittings. Since the car has some "mileage" :-) , the clamps have left an imprint on the hoses and I found myself trying to find a spot on some hoses where the claps would provide a tighter fit. I must admit, some clamps were not as firm as I would like. This weekend, I am going to take it apart again, replace some hoses with new clamps for a tighter fit, and then check for vacuum leaks.

also, the car does not stall when pumping the brake hard while idling.


Well DOM, no go this weekend. I replaced most of the claps on the vacuum hoses. Then I sprayed each with carb/throttle spray for leaks. Did not get to 18 miles before the CEL light came on with same code. Guess I will have to checks CorollaMikes' website ... Dang this is very frustrating.

Any cracks or visible warp on the intake manifold? Cracks or other damage on the airbox, piping leading to the throttlebody? Might have to use a leak detection dye + revealer / set the intake manifold on a perfectly flat surface/straight edge to check for warping. I've read on other forums of a similar situation, very stubborn P0171 lean condition - turned out the manifold was cracked. Didn't appear under inspection - but when they pressure tested it - leaked like a sieve.

Bad PCV valve (stuck open) can also cause this to bring up a P0171 - usually shows up as a very dirty throttlebody. Can be an intermittent sticking - cause more diagnostic headaches. Same with the replacement MAF - make sure it has a good seal in the air box.

Sticking injector, faulty igniters, even a bad tank of gas can pop up a P0171. Might be worthwhile to fill the tank with premium fuel (helps resist detonation) - add a decent fuel system cleaner and run the nuts off the car on the highway. This is what helps on my 8th gen - as it seems to pop up either a P044x EVAP family of codes or P0171 lean code almost always before I have to smog the car.

Last time it did it - the CEL came on as I was waiting in line to get smogged! After I finally fixed it - the car was trouble free for two-years, no CEL, until last weekend when I was thinking of smogging it a bit early. Four different DTCs!


OK fishexpo101 ... good stuff. I replaced the pcv valve earlier this year, but will check again. Although I have used tektron fuel cleaner for years, I will put in some premium gas with cleaner. I will start here. I don't believe I have used premium gas since I purchased in 2006. if this does not work, I will move to intake manifold and airbox as culprit. will keep everyone informed ...


O.K. fishexpo101, dom, corollamike, and all you P0171 enthusiast ... I believe I solved this code problem. This is a longgggg story so get you coffee, sit back, and relax.

since my last post, I took the car to a repair shop that would give me an exact diagnostic on my car's p0171 code. This repair shop said the problem was my fuel pump but they could not repair at the time (it was Thanksgiving week).

I decided to take the car to the Toyota dealer on the belief that the dealer had the exact tools to pinpoint the problem since I had done everything I could on the "air" side. The dealer said the injectors were bad (hello fishexpo101 and corollamike). However the price was very expensive ($900 including the $95 diag).

I was very apprehensive about messing with gas. But, I found a Youtube site on how to replace the injectors and also how to get to the fuel pump assembly and decompress the fuel system.


These are the three videos (as well as the Haynes book) I used to replace the injectors. A word of caution!!!!!!!!!!

The last video recommends using o-rings from Toyota. Like a fool I did not originally do this. I purchased refurb injectors with o-rings and separators. THIS WAS A BIG MISTAKE. I followed the the videos to depressurize the fuel system, took off the old injectors (they looked really bad), put in the refurb injectors with o-rings/separators, put everything back and took car for a spin. After 30 miles I smell lots of gas, stopped, and found the injectors squirting out gas like crazy. I quickly ran from the car praying the car would not blowup (I had stopped at a gas station to get coffee).

long story short, I sent back the injector with the funky o-rings to RockAuto who quickly gave me a refund after they viewed the pictures I took of the o-rings. I ordered Denso injectors and purchased o-rings and separators from Toyota. The Denso injectors came with o-rings which looked and felt a lot stronger than the o-rings that came with the refurb injectors. However, the Denso did not come with separators.

Since the replacement there has not been ANY gas leaks. Takeaway for me .... Stick with Denso parts for critical system components (and follow directions from people who appear to have some knowledge).

There is another twist. I have received another CEL code It is p0420. But, after 50 plus miles, the code goes away and comes back after 500 to 800 miles. I will open up another forum for this problem.

Thanks for all the advise you guys ... see you in the next installment.


Good stuff - glad to hear that you got this one licked! P0171 lean condition can manifest in a number of different ways - but this one seemed a bit tougher than most, especially on a 9th gen.

Wow - $900 for injectors! Talk about steep - lots of times the injectors are OK, just need to be cleaned. But given the amount of miles you've driven in that short amount of time - very possible that some of the injectors were close to their designed life cycle. As most injectors are typically designed for a billion cycles, for most - this lasts the life of the car, assuming they drive 10-12K year, hold onto the car for no more than 25 years - 250K-300K mile service life.

But a P0420 code on a 9th gen? That is pretty unusual - my money is on the downstream O2 sensor that is faulty. Though with that many miles - it is possible that the catalytic converter is at that end of its service life.


fish, at what point do you put the corolla down ??

as a bean counter, I would imagine there comes a time in the life of the car,

the parts are more expensive than the expected life expectancy of the car ??

live with the code without sinking more $$ until it drops dead ??

but when ??

Difficult question. I've been fortunate so far. Actually bought a code reader for my Crown Vic, never needed it on the 2007 Corolla. New cars are expensive to buy and expensive to insure Rebuilding an engine and trans is still less than buying a new car. I'm going to see how long we can keep this car. Unlike my old Saab 99 Turbo, I expect it to nickel & dime me at some point, but the nickels & dimes won't be huge as on Swedish cars.


why worry about codes???

at thus point..if it stops running or is unsafe..then put some money into it..

how can a 280k car not have codes ???

probably a multitude of aging parts that are still functional...yet not perfect...


I live in great white corolla 12 yrs old..I wasted $$

worrying about what the efficiency drops 1 %

in my case..I think I will never recoup the 300 I spent at dealers fixing it...last year..

even if I only paid for the parts..never recoup for life of car...

from now on..either its safety issue or damaging condition.. otherwise I'm going to be cheap..really cheap..