Check Light On...p0171 System Too Lean (bank 1)

[kthan]

I got check light on in my 00 RX300 (currently only 21000 miles) and ran a computer scan at Auto Zone today.

The error code is P0171..System too lean (Bank 1). It looks like Oxygen sensor goes bad/dirty (couple of members reported the light turned off after just cleaning the sensor, not replacing it). Would this diagnosis pretty accurate? Or could it mean there is something other than O2 sensor wrong?

I did not find any suspicious symptoms but I recently had occasional knocking sounds. I thought this sound because we used 87 gas for couple of tanks. It is not constant knocking (just on and off for about 3-5 minutes). Today I made the tank almost empty and then refuel with 89. With 5 mile driving, the knocking sound was gone. I don't know if the knocking sound is related to this issue or not.

If it is a problem of Oxygen sensor, I would be surprised because the current mileage is only 21000. I found some other posts but they are all over 60-70K miles.

Also, please advise me how to handle/fix the issue (how much would be the parts and labor?). My car is already out of warranty, but I found some (oxygen sensor) cases that the dealer services fixed it for free (as "good will gesture") because of its early failure. I am wondering if I can ask them about my car.

Another concern: if the oxgen sensor goes bad, is there any possibility that the other related parts (like other 02 sensors) go bad in near future (Or, the failure of a (emission related) part has nothing to do with the continous problem of the other related part)?

I did not purchase a extended warranty yet because the current mileage (21000) of my car is so low. But, I started to be very concerned about reliability of my car due to the check light problem and other issues (I posed it next to this thread).

[kthan]

While waiting for the posts, I found that P0171 may be related to Mass Airflow Sensor. Can anyone clarify/help me out?

[thunderbirl]

While waiting for the posts, I found that P0171 may be related to Mass Airflow Sensor. Can anyone clarify/help me out?

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I had the same error, took out the MAF sensor, and noted that it was kinda dirty/gummy. I cleaned it with a spray and have had no recurrence for the past 20K...

I hope you might have the same luck....

[lexus_romeo]

My lexus dealer told me that my $465 bank one sensor needed to be replaced because I was putting in 87 gas. I am now putting in 89 and my knocking is gone. I have 80K miles now.

About a year and a half ago, I had 02 sensor replaced (covered under dealer warranty).

99 RX 300 AWD

[jgr7]

I always use 87 in my 00 RX and no knocking. If you were having knocking your knock sensor is not working properly to !Removed! the timing which may have led to an improper fuel-air mixture which could have ruined your bank 1 sensor.

Jeff

[riwyle]

I had this code, cleaned the mass air flow sensor, was able to then clear the code and it has not returned in last 5k miles. I remember somewhere on this forum seeing instructions and photos of how to do the job. It is very easy. Maybe someone can tell you where to find that post.

[Booyah]

Wow, you dont drive to much do ya:)

[AmFam]

A vacuum leak will cause the same code fault. What happens is that too much air gets into the system, the O2 registers that there is too much are and it pops the code for to lean. In reality the fuel is the exact same amount as when everything is good to go. The vacuum leak creates a false code as far as the fuel mixture/ratio goes as it is getting addition air into the system.

With domestic vehicles this is mostly caused by a vacuum line and occasionally an intake gasket leak.

You can find the vacuum leak by having the engine running and spray Carb cleaner onto all the vacuum lines and then where the intake seals to the engine. If the engine either stumbles or the RPM's rise you have found your leak....

Save your money and don't buy the O2 Sensor until you have eliminated the easy stuff first....