This might be a good place to find some answers:
Technical Articles
Toyota Series - Engine Performance OBD
20 EFI#1 EFI System Overview.pdf file size 349KB
21 EFI#2 Air Induction System.pdf file size 500KB
22 EFI#3 Fuel Delivery & Injection Controls.pdf file size 727KB
23 EFI#4 Ignition System.pdf file size 435KB
24 Engine Controls #1 - Input Sensors.pdf file size 793KB
25 Engine Controls #2 - ECU/Outputs.pdf file size 495KB
26 Engine Controls #3 - Idle Speed Control.pdf file size 352KB
27 Engine Controls #4 - Diagnosis.pdf file size 446KB
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