fuel trims

What is a fuel trim? What kind of car?

been driving the 07 caravan for a month, 100 miles a day, I work 50 miles away from my home. still ltft is at 0. stft are at -15, both banks equally.

This seems to have started right after the fuel injectors were replaced with new ones, O2 sensors are new, fuel pump is new, cam and crank sensors are new, All done at the same time. ill be dam if I can find the problem, I also did ECU relearn, disconnected the battery ect. still ltft stuck at 0.

updated it 2 weeks ago

I really don't know much about KAM circuit, the guy that done the work said he didn't do anything like that, he just undid the battery did the work and hooked the battery back up. If I get my ECU flashed or updated will I get my ltft back?

Person did not use saver tool, think ill try getting it reflashed and update you on it, thanks for all your help.

UPDATE Very strange, the ltft came back out of know were, wish i could explain why but i cant.

Makes sense because I only use the van to go to work and back / 99% all highway driving.

Another question, Can you have a rich condition from some kind of vacuum leak / no codes/ fuel trims- ltft is negative 16 and short term is negative 4, now from what I always here is that a vacuum leak will only cause a lean condition but my instints say that it is possible to have a rich condition vacuum leak, maybe through evap hoses or something, possibly a bad purge valve or ldp.

this is a 3.3 engine, map sensor bolted directly to intake plentum, if a leak I would think that the map sensor would see a higher air and increase the fuel.

So i ended up getting a p0455 large evap leak code, this may be why fuel trims are negative, going to fix evap leak and update on fuel trims.

i failed to mention also that this is a flex fuel vehicle.