angmedic91

iTrader: (5)

Ok, well, I searched this forum regarding a CEL for code P0171. There is alot of info regarding this code, but hard to figure out what caused the code to come on and how to resolve it. I have a 1998 Lexus ES300 with about 148,000 miles and I also am due for a California smog check. Can anyone help me figure out how to fix this code, trying to avoid taking it to the dealer for repairs. Thank you.

DixonPai

iTrader: (3)

i just got that code too, but i cleared it and will see in couple days if it comes back on. ill see, going to mechanics on Saturday to get alignment, ill ask him and see whats up. But if you can get an answer quicker that would be great

masagsxr

What does that mean?
Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.

Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.

Symptoms
You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

Causes
A code P0171 may mean that one or more of the following has happened:

* The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
* There could be a vacuum leak downstream of the MAF sensor.

Possible solutions include:

* In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
* Inspect all vacuum and PCV hoses, replace if necessary
* Check for a dirty fuel filter and proper fuel pressure

angmedic91

iTrader: (5)

Dixon, I have cleared mine in the past, but I didnt know what the code was until now. I bought a code reader and finally was able to have the CEL come on and I scanned it and got the P0171 code. I have an aftermarket intake with a K&N cone air filter. I read this could be the culprit, but I have also noticed that I get the CEL during hot days, above 90 degrees. Dont know if this makes a difference or not. I have cleaned my MAF in the past, just wonder if I need to replace the MAF now, maybe its faulty now. I just hate to guess what it could be, especially since I'm past due on my smog check and need to get a smog ASAP, dont want to get pulled over for expired tags.

This is valuable info, thanks bro. I did change all three of my O2 sensors last year. I did recently clean and re oil my K&N filter, so that may have caused the oil to hit the MAF sensor, but I have cleaned this sensor in the past and still got a CEL, may be a faulty MAF sensor. I may need to replace the sensor now. I also replaced the OEM gas cap with a brand new OEM gas cap. I replaced the PCV and gasket last year. The only thing that hasnt been done and ive been needing to have done is the fuel filter replaced and fuel system flush and cleaned.

Maybe I should just have the dealer look at it and fix it, at this point I'm still guessing on what it could be. Thanks for the info anyway.

angmedic91

iTrader: (5)

Update on my CEL,

Well I called my local dealer and told them what my code was, the service guy thinks it might be my O2 sensor, but I told him I had them all replaced last year, and that I had them install my bank 1 O2 sensor last year. He asked what brand of sensor and I said Bosch and he told me they use Denso. Dont know if that makes much of a difference. He then stated it would cost between $60-120 dollars to run a diagnostic. I then told him my code and then he figured it might be my O2 sensor and if it is, it would cost $450 to resolve.

Also, on my way home early this morning, around 3am my CEL went off on its own, I have not done anything to get rid of the CEL except drive it. I have noticed the CEL comes on when the temp. is above 90 degrees and it's been hot here in the L.A. area. This morning the temp was about 72 degrees. Why did my CEL go off. I ran a check on it using my code reader and now it shows same code, but now as a pending status and the CEL is off. What is going on. And I need to get it smogged. Can anyone help with my situation?

Thank you,

masagsxr

Maybe you have a vacuum leak somewhere. This could also throw off the O2 sensor reading.

Causes
* There could be a vacuum leak downstream of the MAF sensor.

Possible solutions include:
* Inspect all vacuum and PCV hoses, replace if necessary

Those above are cheap fix. I think its worth looking into. The $60-120 diagnostic the dealer is asking is way more than to buy those parts above.

angmedic91

iTrader: (5)

Well, I called my local Toyota dealer and they told me a diagnostic check would be around $125.00, but that would be applied to the cost of repair. They stated their labor and parts are cheaper than the Lexus dealer. I told him my situation, he believes it could be my O2 sensor or my Cat. Convert., but would not know until he hooks the car up to the computer and monitors all my sensors. I figured since the car is there, might as well have them change out my fuel filter and do a fuel system clean; and drain and flush my brakes. My car is gettng close to the 150,000 mile service mark. Any other suggestions would be appreciated, otherwise I will update this thread with the outcome of my service repair.

masagsxr

i see.. I guess you really dont have any other choice since the car is there and getting worked on. I estimate your total bill to be around $800 for all the work you mentioned.

Yeah, please do keep us updated.

angmedic91

iTrader: (5)

Well, I figured since I need the fuel filter changed and the brakes flushed, I might as well have them repair the CEL. Plus, I dont have time to figure out what is wrong, I'm past due on a Smog Check. If if wasnt for the smog check, i would slowly check and replace things that would/could be wrong. According to your info maybe my MAF isnt functioning properly and that could cause my P0171 code. I researched that a new MAF would cost around $120.00 dollars. I'm able to do some repairs on my own, but dont really have the time and if it is the bank 1 O2 sensor, I cannot get to it, im just to big to get to it, so I would have to have the dealer replace it anyways.

angmedic91

iTrader: (5)

Well, took my car to the Toyota dealer and had them check the CEL and perform other services I had on my list to do. The diagnostic test revealed that the CEL was caused by one of two things. First, my MAF sensor was not reading correctly because of the oil from the K&N cone air filter. I read on here that the K&N filter can wreck havoc on our cars. The dealer removed and cleaned out the sensor and replaced back in. The second issue was my valves. The dealer stated the tests were showing my valves needed adjustment. I havent had that done before and per Toyota, should be done every 60,000 miles. My car missed its 120,000 mile service by my sister who was the original owner, so I figured have them do it too. Also, needed to have the fuel filter replaced, hadnt been done in a long time, if at all and the last thing I needed done was the brake fluid drained, filled and bled. The fuel filter and the brakes, were on my list of, To Do Items. The first two service issues were related to my CEL. Total damages: $928.00

The car has more ponies now after the valve adjustment, more kick on acceleration and now I'm hoping more MPG, been averaging 23 MPG, so I'm hoping for more. Replaced my K&N filter with a dry foam filter that came with my Weapon R intake system. No more wet filters in my car. And my brakes feel better, no more spongy brakes, now when I start to press on the brake pedal, the brakes are quickly engaging, before they felt spongy, like I had air in the system.

The last thing I need done is a Calif. Smog Check, will get that done this weekend, after I've driven the car awhile. Hope this helps out in regards to a resolution of a CEL, P0171.

masagsxr

Glad everything are fixed..

Yeah, K&N Filter can do that. Some people clean it but soak it with the oil and put it in right away. It should just be coated and hang a bit to dry... I was almost dead on with my estimate ..... Sounds worth it for all the job. I hope they did do the valve adjustment. That itself was already a pretty big job.

DixonPai

iTrader: (3)

AW MAN $928 HAHAHA what you described that was fixed was pretty much what i have NOOOO but thats good everything is fixed

angmedic91

iTrader: (5)

Yup, the valve job alone was $550.00. I would believe they did everything, my brakes do feel different, noticed level change in the brake fluid resevoir. Also notice my intake chrome tube is a lot dirtier and the MAF gasket is more visiable than before and the engine has a smell of burnt chemicals, sort like after they change your oil. So, I would assume they actually did what they charged me, plus I notice more kick on acceleration. Next, is my standard every 5,000 mile oil change in about a month or two and I was also told my transmission fluid is a little brown. New thing to take care of when I change my oil. I even had the tranny fluid dumped, flushed and filled a year and a half ago by the Lexus dealer. I cant believe its turning brown again, only after 15,000 miles of driving. Oh welll................

LeX2K

According to some over @BITOG, Toyota/Lexus brand fluid tends to turn brown quickly. I have the same experience, and won't use it again.

masagsxr

You can do the tranny yourself if you want to save a lot of $$$. The ATF Type IV is only $3.49 at the dealer. There is a DIY at Lexls.com that you can use as a guide. You'll probably need about 12 quarts to completely flush it. I think dealer will charge about $150+ for that job.