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Disable the Long Term Trim?

Practical Reflash Tuning

Discussion and questions related to the course Reflashing


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How do you disble the Long Term Fuel Trim on a OE ECU? And that advise at the end to disable the LTFT was ONLY WHEN TUNING open loop operation right? Then you activate them again to leave everything normal. Am I Right? Thank you!

Hi Jorge,

What software and platform are you working with?

The ability to disable LTFT will vary depending on the software you're using. My personal preference in the GM reflashing world is to disable LTFT and allow the STFT to correct any small fuel variations. This in my experience maintains a more consistent open loop fuel delivery (as the LTFT can remain active in open loop operation). There are plenty of tuners who would argue the opposite though so it just comes down to your own preference and experience. The STFT and LTFT need to be disabled when you're scaling the MAF sensor or the VE table if you're running SD, otherwise they will correct any error between your measured and commanded AFR.