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P0171 - System To Lean (bank 1 )


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#21 ssmall

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Posted 11 October 2004 - 06:03 AM

I've been having the same problem as all of you. Similar story. 97 Camry. The check engine light came on about two years ago and Toyota replaced the MAF sensor as it was under warranty.

Three months ago the light comes on, I bring it in and they find code P0171 (lean Condition) Freeze fame shows very high trim values. Check that sensor is latest part. Sensor reacts normal to spike and active tests. Cleans MAP inlet filter and road tested. Trim display is now normal.. They note I have an "early ECU" compter.

I get the car back and after a few week that dam light comes back on. I buy some fuel injector cleaner and disconnect the battery to clear the light. Drive for a month then the light comes back on. Disconnect the battery again.

I take it into get smogged and it fails. I take it back to the dealership and get a full service for 105k. My disconnecting the battery had left no codes to refer to. While in line to pay, someone else was having both A/F sensor and the computer replaced - under warranty.....some coincidence.

I go back and am able to pass smog. Two weeks later the light comes on again. I do nothing this time but drive around with the light on for about a week and a half.
Then the light goes off. Comes back on an hour later. I do notice that just before the light comes on that there is a slight hesitation, split second, in the power. I do start to feel these very slight hesitations while drive. They are barely noticeable and the car seems to drive just fine.

I am bringing in the car for the last time to Toyota. With all that I am reading, I think there is a major manufacturing defect in the air/fuel sensors and the computers that they are not be honest about. I'll follow up and let you know what happens

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#22 ssmall

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Posted 14 October 2004 - 12:24 AM

OK here is my follow up to my previous message

This A/F sensor and computer problem is widespread. Toyota probably does not want to admit it. There probably is a malfuction in the match up between the computer and the sensor (feedback loop) that is preventing the air and fuel ratio to be mixed properly. I would also venture to speculate that this problem involves other Toyota products other than Camry, that use this same subsystem for fuel delivery.

I have to say that the dealership where I take my car was very fair and replaced both the A/F sensor and computer. It turns out that the 97 Camrys have an old version computer that is related to the problem. When I spoke with the master mechanic he told me that after taling with the factory, Toyota's recommended fix was to replace both the sensor and computer (over a $1000 in parts alone). Much appreciated was that he got the parts to be covered by Toyota and I just had to pay for the labor only. When this problem first occured I was under 100k but am now at 104k. This was the third time I had brought the car in and had already spent over $300 in labor.

While I was waiting in line again the service person at the front desk was on the phone describing to the customer that they had a check engine light on with a lean condition, and that they were going to try to clean the A/F sensor........"Yes maam.... that would account for the split second hesitation in power..........

The master mechanic said that one of the other mechanics had my same car (97 Camry) and he too had the exact same problem - hesitation in power, followed by check engine light, followed by lean condition codes. Also said that replacement of the computer and sensor resolved the check engine light from coming on but he still gets that split second hesitation in power.

Notes from the service write up: Code P0171 (system too lean) code P1135 (A/F Sensor heater circuit malfunction bank 1, sensor 1). Tech tested A/F sensor on scan tool and sensor is not responding to lean command. Tech prelaced ECU and A/F sensor.

Hope this information helps. This might end up in the news at some point as a product recall due to defective design.

#23 Kanadakid

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Posted 21 October 2004 - 07:22 PM

ender above has the goods on the 171 bank one code. I too missed the internal wires inside the MAF sensor. Now I know !!!

saved me some bucks on this gig !!


Kid

#24 Matt007

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Posted 23 November 2004 - 07:34 PM

I too am having the P0171 problem. I have a completely stock 2000 Celica GT with 95K miles. The CEL recently came on with error code P0171. Coincindentaly, this happended about two days after I got it back from the dealership to have a brand new transmission and clutch installed, so I'm wondering if something in the exhaust system is not put back together correctly.

I cleaned the MAFS, cleaned the throttle body and IAC valve, replaced the PCV valve, and visually inspected any vacuum hoses I could without taking anything apart. I reset the ECU, but the CEL came back shortly.

I then took it back to the dealer who did the transmission work, who said that it is running lean, but only at idle, and that the O2 sensors and MAFS are fine. They think it's an "intake leak", but want to keep it for a day or more to diagnose.

I'm not ready to give in just yet... I'll try running some injector cleaner, and maybe look into replacing the fuel filter. If anybody has any new updates, please post them. :help:

#25 GT4 BOOSTER

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Posted 24 November 2004 - 11:07 PM

http://www.obd-codes...neric/p0171.php

#26 Joe Cerda

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Posted 30 November 2004 - 07:44 PM

I too am having the P0171 problem.  I have a completely stock 2000 Celica GT with 95K miles.  The CEL recently came on with error code P0171.  Coincindentaly, this happended about two days after I got it back from the dealership to have a brand new transmission and clutch installed, so I'm wondering if something in the exhaust system is not put back together correctly.

I cleaned the MAFS, cleaned the throttle body and IAC valve, replaced the PCV valve, and visually inspected any vacuum hoses I could without taking anything apart.  I reset the ECU, but the CEL came back shortly.

I then took it back to the dealer who did the transmission work, who said that it is running lean, but only at idle, and that the O2 sensors and MAFS are fine. They think it's an "intake leak", but want to keep it for a day or more to diagnose. 

I'm not ready to give in just yet... I'll try running some injector cleaner, and maybe look into replacing the fuel filter.  If anybody has any new updates, please post them.  :help:

 



#27 jasper

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Posted 08 January 2005 - 09:42 AM

i am planning to buy this used 2000 Toyota Corolla. The car is great except that the engine light is on and the 171 code Bank 1 appeared per diagnostic check. can you guys advise me if it's ok to buy that car or it's better if i don't acquire it? do you think that is a major problem for me in he future?
i will appreciate your honest advise on this as this is my first experience in buying a car.

#28 GT4 BOOSTER

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Posted 08 January 2005 - 03:31 PM

http://www.obd-codes...ygen-sensor.php

#29 [gato]

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Posted 17 January 2005 - 08:53 PM

...
Then the light goes off. Comes back on an hour later. I do notice that just before the light comes on that there is a slight hesitation, split second, in the power. I do start to feel these very slight hesitations while drive. They are barely noticeable and the car seems to drive just fine.
...


Hy everybody, my first post :D

Sorry if my enlish is not to good :huh:

My father's car (Corolla 2000 1.4vvti) has the same problem, the light on and the slight hesitation in aceleration.
He goes to toyota and they substitute the O2 meter, but the car continues with the same problems.

Once i drive the car and pushed all the shifts to 4000 rpm, and the car starts to get less problems of hesitations, but my father don't acelarate too much.

One more thing, this problems appeared more or less one year later then my fhater buy the car, but happened rarely.

I'm thinking to make a reset to ECU, mainly because of the symptoms that ocure when I drive de car.

One question off topic, to reset ECU? disconnect the negative battery, wait 5 minutes and press the break pedal?

[][]

#30 sandymac

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Posted 06 May 2005 - 03:16 PM

I have a 2000 Avelon. The CE light came on last week. An auto parts store ran the codes and it came up P0171 Bank# too lean. I cleared the light and it came back two days later. Car runs fine and suddenly I'm getting 30 MPG. The best I ever got was 25 MPG before the light came on.
I think I'll put up with the light and enjoy the gas savings.

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