Fuel level sensor

These are ideas only as there are many things that could improve gas mileage.
When was the last time you had a tune up? (Spark plugs check for bad sensors . When was the Air filter changed..
do you always check the air pressure in the tires. Low tires can bring your mileage down five miles per gallon or more.
Do you drive with fast starts and stops.
Do you run short trips? Short trips does not let the engine warm up to the right traveling temperature. I live in town and I get about 15 miles per gallon in town but if I drive 20 miles or more I get 24 or more with my Buick.
You will get less mileage if you drive in real cold weather.

code p0170 refers to two problems
fuel trim bank 1 --malfunction
heated oxygen sensor(HO2S) 3 bank1 --circuit malfunction
for the first error==causes-- intake leak --AIR system---fuel pressure /pump---injectors--EVAP canister purge valve---HO2S
for the second one ===causes=--wiring--HO2S---ECM
The explanation of fuel trim is long winded and you may get some typo errors but I think that you will get the idea
short and long term fuel trim refers to the strategy used to reduce exhaust emissions after a basic computation of injector period, using engine load as a major parameter
both front and rear oxygen sensors signals are used to fine tune the air/fuel mixture by increasing or decreasing the injection period =/- 25% above or below the basic level
any fault requiring a correction beyond this level will result in a fault code being logged ( in this case p0170)
the fuel trim will oscillate the injection period =/- 5% above or below the mean level level A
manufacturing and in-service tolerances of load sensors (MAP,MAF, VAF) and injectors in particular and faults such as intake leaks( vacuum hoses from vent controls and transmission) will affect the air/fuel mixture and cause the trim to compensate
an air intake leak for instance would increase the injection period increasing for example to 115-125%. this level will also oscillate +/- as before level B
this new short term fuel trim level will be stored in the ECM if it is established as a new basic mixture level
It will become a long term fuel trim correction and results in the correct mixture level immediately after starting, even when the HO2S has had sufficient time to heat up
Now having some idea of what trim is, you will see the necessity of repairing any problem sensors ,air leaks ,vacuum leaks
You will also probably understand the reason of why an engine after running short runs ( city driving) feels that it gets more power and better economy after 1/2 hour on the open highway
The ECM resets the trim to the new load power settings and that becomes the new trim

More than likely the fuel tank level sensor (which is located inside of the fuel tank is seized. You will have to have the fuel pump and level sensor replaced.

Could be fuel pump is going out. Its getting hot not working properly and when it cools down it works right again for a short period. Ive seen this happen several times.

Check for a leak in the fuel system, especially around the fuel pump and any fuel line that may have been moved during the change. Another possibility is dirt in the fuel injectors is keeping them open so they dribble in too much fuel - you may smell unburned or incompletely burned gasoline in the exhaust when the catalytic converter is cold. A problem with the ignition (bad plug or cable) will also do this, but the engine would probably run a bit rough under load in this case.

If you are getting the mileage from an instrument panel mileage indicator, have you calculated your mileage per gallon with the amount of fuel put in the tank (from the vendor pump) divided by the odometer difference from the last time you filled? Perhaps there is a problem with the fuel level sender and it's reading low.

if dash gauge is still bouncing ,replace fuel level sensor. some are replacable some you have to replace the whole fuel assembly

Definition of Diagnostic Trouble Code P1346 Audi: Ignition Coil Power Output Stage 3 Short to B+ BMW: Misfire During Start Cylinder 3 Buick: Intake Camshaft Position [CMP] Sensor System Performance Cadillac: Intake Camshaft Position [CMP] Sensor System Performance Chevrolet: Intake Camshaft Position [CMP] Sensor System Performance Ford: Fuel Level Sensor B Circuit GMC: Intake Camshaft Position [CMP] Sensor System Performance Lexus: VVT Sensor Rang/Performance Problem (Bank 1) Lincoln: Fuel Level Sensor B Circuit Mazda: Fuel Level Sensor B Circuit Mercury: Fuel Level Sensor B Circuit Oldsmobile: Intake Camshaft Position [CMP] Sensor System Performance Pontiac: Intake Camshaft Position [CMP] Sensor System Performance Saturn: Intake Camshaft Position [CMP] Sensor System Performance Toyota: VVT Sensor /Camshaft Position Sensor Circuit Range/ Performance Problem (Bank 1) Volkswagen: Ignition Coil Power Output Stage 3 Short to B+

Trouble Code: P0171 (3.8L V6 VIN 1 Auto)
Fuel Trim System Lean (Bank 1) Print this code data Number of Trips to Set Code: 2
OBD II Monitor Type: CCM Details
Indicators: MIL Details

• Fuel Details
• MIL Details

Trouble Code Conditions:
DTC P0101-P0103, P0107, P0108, P0121-P0123, P0130-P0138, P0140, P0141, P0201-P0206, P0300, P0401-P0405, P0410, P0440-P0446, P0506, P0507, P1404 or P1441 not set, engine started, vehicle driven at less than 82 mph at 550-4000 rpm, BARO sensor over 70 kPa (10.1 psi), ECT sensor from 68-230ºF, IAT sensor from 64-158ºF, MAF sensor from 2.8-150 gm/s, MAP sensor from 16-105 kPa (2.6-15.2 psi), fuel level over 10%, and the PCM detected the Long Term fuel trim value was more than +20% for 6 seconds. The PCM controls the air/fuel metering system to good overall fuel economy, driveability, and emission control. During open loop, the PCM determines fuel delivery based on sensor signals, without the oxygen sensor input. During closed loop, the PCM adds oxygen sensor inputs to calculate Short and Long term fuel trim fuel delivery adjustments. Short Term fuel trim values change rapidly in response to changes in the oxygen sensor signals. Long Term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1.

Possible Causes:

• Air leaks in intake manifold, exhaust pipes or exhaust manifold
  
• Fuel control sensor is out of calibration (ECT, IAT or MAF)
  
• Low fuel pressure (fuel filter clogged, pressure regulator failure)
  
• One or more injectors restricted or pressure regulator has failed
  
• HO2S element is contaminated, deteriorated or has failed
  
• Vacuum hose is disconnected, broken, leaking or loose
  

Troubleshooting:2002 Buick Park Avenue, 3.8L, P0171

their are several possibilities sending unit is malfunctioning or a short in the wires, if 2006 is it not still under warranty?

khooper, in another forum, told me that "Chevron Techron Fuel System Treatment Plus can remove harmful sulfur deposits from the sending unit and a filmer agent that can prevent the deposition of said sulfur"

My 05 Trailblazer LT 2WD.
Erratic readings, and when the fuel level was below 1/2 full, the needle would sit on "Empty" with the amber light staying on.

So I went to a dealer, they replaced the fuel level sensor (p/n 19177712 SEN KIT 3.107 $118.62) with labor $270.00 for a total of $398.86 this appears to have fixed it for now.

I also talked to another mechanic who blames ethanol for these deposits !