Codes P0171 and P0447, fuel gauge and random check engine light?

2009 NISSAN MAXIMA
110,530 MILES • 6 CYL • AUTOMATIC
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All of my gauges work except the fuel gauge, it is dropped way past E, however my digital gas mileage reader works. Do I need to change the entire cluster for this issue? I’ve read some things that say the fuel sending sensor/pump can be the culprit, but I just don’t know enough about cars to confidently spend money on a pump and that not be the issue. Also, if it is the cluster, and I purchase a used one, since it is digital, will my mileage transfer to the replacement cluster?

My second question is, my check engine light keeps come on- on its own for several days then goes off (I have no issues driving or no noticeable changes when on or off) I have already changed the oxygen sensor, but I am getting that same code P0171 but also getting P0447 when the check engine light is present, the second code is relatively new. Could you help me out here?
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Jan 2, 2025 at 12:18 PM
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CANNON1349
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Hello,
If the car is full and the gauge rests at E, it doesn't necessarily mean it's a cluster issue. When you first start the car, do all of the gauges do a "test" and go to one side and then the other? If so, it's not a cluster problem. However these cars do frequently have this issue with the fuel pump, we will need to rule it out. If you do decide to replace the cluster, your mileage should transfer over as it is stored in the PCM. The code P0171 does not point to a bad O2 sensor, the definition of the code is Bank 1 is running too lean. Let's do a quick test, if you clear the codes with the car running, does the fuel gauge seem to work, then go down again?

Please let us know,
William
Jan 2, 2025 at 4:45 PM
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Gas Gauge moves on startup but it’s still way down past E and never goes to E, It stays down, the other gauges do move. When I fill up, it will move up towards E, I’ve noticed it has gone to a quarter tank reading one time, but never more than that. If I clear the codes nothing changes. check engine light will just randomly pop on with the codes I have provided. But again, I’ve changed 1 02 sensor so I’m just not sure what to do here.
Jan 4, 2025 at 6:08 PM
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CANNON1349
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Hello,
The O2 sensor is doing its job if you are getting the code mentioned. This will be a separate diagnostic of how the engine is running to reach a conclusion as to why the code is appearing. Same for the evap code. About the gauge, do you have a scan tool of any kind that can read live data?

If not, you can get one relatively cheap on Amazon, see below:
https://a.co/d/8XNZ1BF

If the gas gauge rests below E all of the time, I suspect you may see a negative value on the live data or another arbitrary number causing it to stay low. This will point to the sending unit on the fuel pump. However, if you know the tank is full and the live data says the level is 100% then we could have a cluster or other electrical issue.

Let us know,
William
Jan 5, 2025 at 8:31 AM
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I fill my tank regularly as I drive frequently, so I always know it’s full when it’s full. The digital gas mileage reader is always on so I can monitor my usage and remaining mileage since the gauge itself doesn’t work. If in the event it isn’t the cluster, what would the other electrical issue be?
Jan 6, 2025 at 10:36 AM
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CANNON1349
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Typically the issue lies within the sending unit of the fuel pump. It is a simple potentiometer with a float and translates the height of the float into voltage and the computer interprets that voltage as a percentage. That's why if we can use a scan tool to see the live data, it will show what percentage of fuel you have left. A failed sending unit will show a crazy number or simply nothing.

William
Jan 6, 2025 at 5:00 PM
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So it’s safe to assume (if I’m understanding correctly) that I need to fix the fuel pump/sending unit to rid the codes I’m getting for 02 and Evap and replace cluster if it the gauge doesn’t correct itself after which?
Jan 13, 2025 at 1:22 PM
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CANNON1349
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The first thing to do is read the live data with a scan tool. Without doing this we are only guessing and throwing parts at the car. Once you can read the live data report back to us and we can discuss it further. The o2 and evap codes are completely separate and different diagnostics from the current problem.

Here is the link for a scan tool that supports live data:
https://a.co/d/8XNZ1BF

Thanks,
William
Jan 14, 2025 at 8:16 AM