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P0172 Code- Help Please

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Old Jan 19, 2019 | 12:45 PM
  #161  
cturboaddict's Avatar
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From: Collinsville, IL
Originally Posted by Oldblue
Short
Term
Fuel
Trim

now why would that be needed to be adjusted?

Shhhh, I’ve got to read up in this stuff

https://www.autoequipment.com.au/ima...iagnostics.pdf
It resets everytime the key is switched to ON. Butttt, when resetting fuel trim (LTFT for this application), you're resetting the STFT at the same time.
Old Jan 19, 2019 | 01:12 PM
  #162  
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In the considered example the computer adjusts to compensate for a failing fuel pump, would that indicate a failing O2 sensor or out of range fuel pressure?
Old Jan 19, 2019 | 04:11 PM
  #163  
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Maybe your tool is different, mine can't "reset" the trims.

Old Jan 19, 2019 | 05:00 PM
  #164  
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Originally Posted by donbrew
Maybe your tool is different, mine can't "reset" the trims.

Yeah, there were more options as well. Can reset fuel trims and reset fuel alcohol content.
Old Jan 20, 2019 | 07:13 AM
  #165  
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Looks like a good scanner for what you need.
Old Jan 20, 2019 | 08:58 AM
  #166  
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Freezing Morning Update

Yesterday the car started and ran flawlessly in the morning. I let the car sit for the majority of the day and as temps plummeted to the teens, around 6pm I tried to remote start (mind you the remote start wouldn't fire the car previously). Low and behold it fired right up.

I let it sit all night long, and it was 12 degrees this morning. Remote start worked perfectly. I drove it around this morning and everything worked great. Tried starting with all accessories running. Tried starting without waiting for fuel pump to prime, and hot and cold starts. All works good.

looks like the mpg has jumped as well.
Gonna give it an oil change and then pull data to confirm it's where it was.

Last edited by cturboaddict; Jan 20, 2019 at 08:59 AM. Reason: Spelling
Old Jan 20, 2019 | 11:13 AM
  #167  
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Yeah!! Fixed, so, what did you do? Trim the fuel trims?
Old Jan 20, 2019 | 11:28 AM
  #168  
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Originally Posted by Oldblue
Yeah!! Fixed, so, what did you do? Trim the fuel trims?
Everything is still kosher this morning.

Resetting the FUEL ALCOHOL CONTENT AND FUEL TRIMS brought the computer back to normal and put everything back to running right.

I'm assuming, that the gas line leak, and probably the EVAP line leak caused the fuel alcohol/fuel trim to get skewed. Resetting and then refilling brought everything back to normal. Fingers crossed this is the final frontier. Now to fix that pesky TPMS light that's driving me bonkers anytime I get in my wife's HHR.

Here's some info on the E85.

E85 Flex Fuel DescriptionE85 compatible vehicles no longer use an alcohol sensor to determine and adjust for the alcohol content of the fuel in the tank. Instead, the vehicle calculates the alcohol content of the fuel through measured adjustments.



The ethanol calculation occurs with the engine running after a refueling event has been detected via a measured change in the fuel level sender output. The virtual flex fuel sensor (V-FFS) algorithm temporarily closes the canister purge valve for a few seconds and monitors information from the closed loop fuel trim system to calculate the ethanol content. This logic executes several times until the ethanol calculation is deemed to be stable. This may take several minutes under low fuel flow conditions such as idle, or a shorter time during higher fuel flow, off-idle conditions.



Air-fuel ratios and the corresponding ethanol percentage are updated following each purge-off sequence. The fuel alcohol content percentage value can be read on a scan tool.



When an E85 compatible vehicle is built, an ECM or PCM replaced, or if the learned alcohol content has been reset with a scan tool the fuel system will need to contain ASTM gasoline with 10 percent or less ethanol content.



A minimum of 11 liters (3 gallons) must be put in the tank in order for the vehicle to recognize a re-fueling event. It is not necessary to turn the ignition OFF in order to have the re-fueling event recognized, however local safety regulations should be followed.



After the re-fueling event, the system registers the amount of fuel that was added, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines if the fuel added was either ASTM Gasoline or ASTM E85. Based on that determination, the system adjusts to the expected alcohol mix in the fuel tank, and then the fuel trim and O2 sensor activity fine tunes the adjustments. The system must remain in closed loop in order for this adjustment to occur. Numerous short trips after switching from gasoline to E85, or E85 to gasoline, can result in driveability symptoms due to the inability of the system to adjust for fuel composition by not attaining closed loop



Old Jan 20, 2019 | 11:43 AM
  #169  
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Enjoy!
Old Jan 20, 2019 | 11:44 AM
  #170  
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Originally Posted by DrLoch
Looks like a good scanner for what you need.
I agree
PS: I click on those links that cturbo posted and they don't pop up.



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