Check engine light on with P0171

[mendenken]

Hi All,
I have camry LE 1999 model(4 cylinder). I have the check engine light on for last few months. I ignored it as there is no problem in use. I have the inspection due by the end of september. I read somewhere that the P0171(System is too lean on bank1) is due to the dirty maf(mass airflow sensor). How can I clean it, is it safe to clean my own.
I heard that is very expensive piece.

Also, I haven't done any filters changed for last 90 thousand miles. Would that be a cause of the "light on"

Any input is appreciated.

Thanks

[RIP]

This won't be identicle to your car but, should give you the general idea: http://www.lexusownersclub.co.uk/kno...v2&id=152&c=11

A little more info: http://www.obd-codes.com/trouble_cod...gen-sensor.php

Download your factory maintenance manual from the Factory Service Manuals thread at the top of the forum. The FAQs thread should also have more info.

MAF sensor should cost $150-$200 for your car. May be cheaper on the net. Maybe Ebay.

[2000izusu]

keep in mind po171 is one of the hardest codes to diagnose for the do it your selfer. could be a vaccuum leak, fuel system problem, maf mentioned above etc... becareful with diagnosis.

[Brian R.]

http://www.automotiveforums.com/vbul...d.php?t=732698

Different engine, same problem to solve

MAF meter resistance and long-term vs short-term fuel trim will determine whether it is the MAF meter or not. Resistance will diagnose ECT sensor.

[artbuc]

Originally Posted by Brian R.

http://www.automotiveforums.com/vbul...d.php?t=732698

Different engine, same problem to solve

MAF meter resistance and long-term vs short-term fuel trim will determine whether it is the MAF meter or not. Resistance will diagnose ECT sensor.

Brian, how will the fuel trim confirm a bad MAF? What will the short term and long term fuel trim be if it is a bad MAF? Thanks.

[Brian R.]

In the freeze frame output, the total of LT and ST fuel trim should be less than 35%. My total in the cited example was 41.3%.

If the fuel trim total is greater than 35%, and the MAF resistance is marginal, then the freeze frame values confirm the MAF meter is probably the problem. This is not a sure thing. There are many possible causes for this code.

[artbuc]

Originally Posted by Brian R.

In the freeze frame output, the total of LT and ST fuel trim should be less than 35%. My total in the cited example was 41.3%.

If the fuel trim total is greater than 35%, and the MAF resistance is marginal, then the freeze frame values confirm the MAF meter is probably the problem. This is not a sure thing. There are many possible causes for this code.

Thanks Brian. Why does your scanner show ST and LT fuel trims for Bank 3 at 100.6%? What is Bank 3?

[Brian R.]

I don't know, but I would guess it is an unused channel. The values are meaningless. Maybe it is used when there is a bank 2 sensors 1 and 2 A/F Ratio - HO2 sensors (dual exhausts).