Fuel Trim Levels. LTFT . What Scanner to reset LTFT?

[asylum]

My 2013 Sierra 5.8l is throwing P0172/P0175.  From my research it appears the LTFT needs to be reset via a scanning too.  I've looked at a lot but before I spend a couple hundred I want to be sure that tool will allow me to zero out the LTFT percentages.  This is the answer I can't find on these products.

Any recommendations for a scan tool that will do what I want?  I was looking at Ancel FX2000 on Amazon.  Any others?

 

Thanks

[CamGTP]

If that is all you were trying to do you could just remove the battery connection on both posts so there is no power going to anything. Leave it that way for like a half hour and then touch the two cable ends together to deplete any reserve, then hook it all back up.

 

That should do a reset on the computer and any codes you have. I doubt that resetting the trims will do anything on a scan tool because they will just reset and go back to the way there were before. If I had to guess it's that the virtual flex fuel is acting up and causing this issue. I've seen it happen before and doing a hard reset on the computer or resetting the fuel composition fixed it. A nice scan tool would be needed to see what the computer is saying for alcohol content in the fuel. A normal reading is 5-10% for regual pump gas and if it's reading wrong it would be saying like 50-70% even though you are not running E85 from the gas station.

[asylum]

7 hours ago, CamGTP said:

If that is all you were trying to do you could just remove the battery connection on both posts so there is no power going to anything. Leave it that way for like a half hour and then touch the two cable ends together to deplete any reserve, then hook it all back up.

 

That should do a reset on the computer and any codes you have. I doubt that resetting the trims will do anything on a scan tool because they will just reset and go back to the way there were before. If I had to guess it's that the virtual flex fuel is acting up and causing this issue. I've seen it happen before and doing a hard reset on the computer or resetting the fuel composition fixed it. A nice scan tool would be needed to see what the computer is saying for alcohol content in the fuel. A normal reading is 5-10% for regual pump gas and if it's reading wrong it would be saying like 50-70% even though you are not running E85 from the gas station.

From my research on the internet and youtube, what you explained is what I've been finding and they have been resetting the fuel alcohol levels with a scan tool.  I have taken the battery terminals off and touched them together for about 30 seconds, and then ran the truck.  The engine light stayed off but eventually came back on with the same codes.  So I thought I might have to reset them with a scan tool.

[Ianf]

I do not believe that you can reset the LTFT or the short term either. I reset the alcohol % with my scan tool (VXDIAG) which hooks to my computer. It keep coming back to 22% or higher all the time. There are some topics here that suggest that the % changes based on engine status after adding at least a quarter tank of fuel. To get the best results you should have an already warm engine and then drive for 7-10 miles after fueling before shutting it off.

 

On another note P0172/175 is NOT caused by alcohol % as a general rule, you must have another issue, like a manifold leak. I had a P0171/174 AND a bad fuel trim and high alcohol% (40%). Resetting the Alcohol percentage did not fix the codes and I later found a small vacuum leak using a smoke test. Search the internet for P0172 for your engine for a diagnostic routine and follow it. You will find the problem.

 

[sefiroxx]

FT are a report on what the ecu did. It's a after action report and is not used in calculating future FT. Future FT settings are based on:
- open/closed
- TPS
- MAF
- RPM
- O2
-Alcohol %

[swathdiver]

On 10/7/2020 at 8:23 PM, asylum said:

My 2013 Sierra 5.8l is throwing P0172/P0175.  From my research it appears the LTFT needs to be reset via a scanning too.  I've looked at a lot but before I spend a couple hundred I want to be sure that tool will allow me to zero out the LTFT percentages.  This is the answer I can't find on these products.

Any recommendations for a scan tool that will do what I want?  I was looking at Ancel FX2000 on Amazon.  Any others?

 

Thanks

Get a Tech-2, your truck was designed to be worked on by it, it will pay for itself in the first repair or near so.