Hi,
Here is some very good documents about Fuel Trim
Don't forget to press "Start"
http://atsnm.com/images/escan/escanf...rt_1_vert.html
http://www.atsnm.com/images/escan/es...rt_2_vert.html
http://atsnm.com/images/escan/escanf...ency_vert.html
http://www.stealth316.com/misc/obdii_fuel_trim.pdf
2011-09-13 Another interesting document (by Toyota Motor USA)
Mode sensors and switches http://www.autoshop101.com/forms/h31.pdf
Temperature sensors http://www.autoshop101.com/forms/h32.pdf
Position sensor http://www.autoshop101.com/forms/h33.pdf
AirFlow sensor http://www.autoshop101.com/forms/h34.pdf
Pressure sensor http://www.autoshop101.com/forms/h35.pdf
Position/Speed sensor http://www.autoshop101.com/forms/h36.pdf
Oxygen/Air Fuel sensor http://www.autoshop101.com/forms/h37.pdf
Knock sensor http://www.autoshop101.com/forms/h38.pdf
Ignition - Overview http://www.autoshop101.com/forms/h39.pdf
Ignition - Electronic Spak advance http://www.autoshop101.com/forms/h40.pdf
Ignition - Distributor and distributorless type http://www.autoshop101.com/forms/h41.pdf
Fuel System - Overview http://www.autoshop101.com/forms/h42.pdf
Fuel System - Injection duration control http://www.autoshop101.com/forms/h43.pdf
Fuel System - Closed Loop & Fuel Trim http://www.autoshop101.com/forms/h44.pdf
There is many others documents from http://www.autoshop101.com/forms/h12.pdf to http://www.autoshop101.com/forms/h27.pdf