To gain a better perspective on fuel trims, think about how “analog” vehicles dealt with changing fuel and air mixtures.
Drivability Issues Fuel Trim Diagnostics
No code diagnostics are some of the most challenging drivability issues.
LTF and STF Fuel Trim Codes P0170, P0175, P0172, P0174
Understanding what parts should be replaced to get ride of these codes.
Not Sure That Air Filter Needs To Be Replaced? Check The Fuel Trim
The kicker with trying to diagnose whether an air filter is affecting performance is to see if the long-term or short-term fuel trims have changed.
VIDEO: Negative Fuel Trim And Fuel Economy
Andrew Markel introduces a case study where a 2004 Chevrolet Impala has no codes, but is getting bad fuel economy.