# Code 0171 and 0174 Need some Help



## Charleee7 (Apr 7, 2005)

What would a person look for if the code reader said 0171 and 0174, lean bank 1, and lean bank 2. What does this code mean, and what would I do to fix the problem. Can someone help me.


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## Puppetmaster (Mar 28, 2005)

Charleee7 said:


> What would a person look for if the code reader said 0171 and 0174, lean bank 1, and lean bank 2. What does this code mean, and what would I do to fix the problem. Can someone help me.


It means your car is running too lean... from the FSM:



> Fuel injection system does not operate Properly,
> the amount of mixture ratio compensation is too
> large. (The mixture ratio is too lean.)


Possible causes are:

- Intake air leaks
- Heated oxygen sensor 1
- Injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor
- Incorrect PCV hose connection

Are there any symptoms? How does the car run?


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## Ran (Mar 3, 2005)

*Engine Lean codes*



Charleee7 said:


> What would a person look for if the code reader said 0171 and 0174, lean bank 1, and lean bank 2. What does this code mean, and what would I do to fix the problem. Can someone help me.


I had the same problem first one 0174 then the other, never both at same time. I replaced both "before" converter O2 sensors, ended up taking it to dealership. They replaced the Mass Air Flow Sensor. Works fine now.
RLee


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## Skippermax (Apr 11, 2005)

*Thanks Charleee7!*

This posting was courtiously placed by Charleee7 on my behalf...I didn't know this forum existed! What a great site. Thank you puppetmaster for your reply!

Let me describe the symptoms of my car. 

When cold, the car is very sluggish, backfires occasionally as if the choke is not on. If I step on the gas too quick, it will bog down and almost stall.

Once its warmed up a bit, it is much better and doesn't give me too much trouble.

I took it to my garage, they changed out an O2 sensor but the engine light came back within 2 hours of driving. They put my original O2 sensor back in. They then cleaned the probe of the mass flow sensor and again the engine light came on within a few hours. 

Codes for lean banks have not changed.

The engine seems to knock quite a lot when accelerating hard but this may be unrelated. I do run ethanol occasionally but normally use regular gas. Charleee7 has suggested to try a higher grade and try some fuel treatment.


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## Puppetmaster (Mar 28, 2005)

Clogged injectors? Not too sure... but I can do some research.... 

If your car can go rev over 2500 rpms, its not the MAF, that's for sure. Since you say it works fine after its warmed up, then it could be the injectors.... but I don't know at this point.


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## lorekcars (Apr 6, 2005)

Puppetmaster said:


> Clogged injectors? Not too sure... but I can do some research....
> 
> If your car can go rev over 2500 rpms, its not the MAF, that's for sure. Since you say it works fine after its warmed up, then it could be the injectors....
> 
> you thinking this checkup can help him, i thing he should be read OXsensor bank one and also find what all tell him


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## Spddracer (Jan 31, 2003)

Most likely a bad Mass Air Flow. Notorious for going bad and causing these codes. As for a earlier post on it only reving past 2500 rpm, The ecm doesn't always go into failsafe when they go bad. Got $10 says it a bad MAF. Oh "shamless plug" I have one for-sale.


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## nickinont (Apr 30, 2005)

I have been reading this thread with interest because I have a similar problem. I have a code 0171, bank 1 lean indication. By the way does anyone know which bank is bank 1 ie is it the front or the back bank? I should maybe compare the spark plugs on both banks to see if one side looks too lean.

The car also has driveability problems, it often hesitates badly under heavy acceleration and won't kick down. It also runs poorly for for about a minute or so after start up. It runs without any noticeable problem under normal driving conditions.

I took it to a garage and the mechanic said the O2 sensor was reading very low, lower than it should read, so he recommended replacing the upstream O2 sensor for the bank 1, which he did. However the same code came back within a day of the replacement and the car still has the same driveability problems. Since it cost me about $300 to get the sensor replaced and it didn't do any good, I am wondering if the O2 sensor replacement was a reasonable diagnosis based on the symptoms the car presented. My reasoning is that the driveability problems indicate that the car actually is running too lean and the O2 sensor was correctly indicating this. I am thinking that it makes more sense to look for a fuel injection problem. Or could an intake manifold leak affect only one bank? Some comments in the thread indicate a mass airflow sensor is often the culprit (in the case of both banks being lean) but I am assuming that this would not be the case for only one bank being too lean. Is this reasonable?


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## titan_213 (May 1, 2005)

bank one is the right(back) head, the guy earlier in the thread was right you will probably need a mass airflow meter, and if it a 2000, you will need the ecu reprogramed cause the new meter is a countermeasure meter.


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## titan_213 (May 1, 2005)

the code doesn't always register both sides, since it is a logic code, it maybe just out of parameters.


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## Revabbott (Apr 30, 2006)

A slightly different circumstance for me. I have a 2000 SE 5 Speed where I periodically have the 0171 code go off, and it will typically reset after a while. I have already (about 2 months ago) replaced all six ignition coils and the rear 02 sensor.

Unlike the other posters with this code, my car is (and has been) running perfectly. I am getting over 29 MPG on the highway, the revs are perfect, and there is no hesitation, knocking, etc... I cannot tell any difference in the car at all, it just occasionally comes on with that code.

Is the car not crazy about the current tank of gas (I use premium, though)? Should I use a good fuel system cleaner? Should I pull the MAF sensor and give it a cleaning? 

Any good suggestions...or should I just ignore it? I have a OBD2 scanner, so if I want to reset the code it is not a problem. I'm a newbie on this forum, and would appreciate some info from the experts.


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## Squid11 (May 1, 2006)

titan_213 said:


> bank one is the right(back) head, the guy earlier in the thread was right you will probably need a mass airflow meter, and if it a 2000, you will need the ecu reprogramed cause the new meter is a countermeasure meter.


So a 2000 spec MAF is still going to require the ECU to be reprogrammed? Is his car not a 2000?


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## reyrey (Mar 31, 2005)

Skippermax said:


> I took it to my garage, they changed out an O2 sensor but the engine light came back within 2 hours of driving. They put my original O2 sensor back in. They then cleaned the probe of the mass flow sensor and again the engine light came on within a few hours.


I have an 01 Max and recently changed my 02 sensor. Had the same problem of the engine light coming back on. As it turns out, the ECU has to be reprogrammed to accept the parameters of the new sensor. Car runs much better after the reprogram and took care of all other SES codes.

I can't say if this will cure your problem but may be worth a shot bringing it in fro reprogramming.


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