str ategy ") ▁and ▁data ▁(" cal ibration ") ▁in ▁the ▁field , ▁if ▁necessary . ▁ ▁The ▁memory ▁module ▁used ▁" Mask ed ▁R OM " ▁( M ROM ), ▁a ▁type ▁of ▁memory ▁chip ▁that ▁was ▁not ▁mod ifiable ▁after ▁manufact ure . ▁ ▁The ▁memory ▁module ▁also ▁featured ▁some ▁switch es ▁that ▁could ▁be ▁changed ▁in ▁the ▁field . ▁ ▁The ▁strategy ▁would ▁read ▁these ▁switch es ▁and ▁ret ard ▁the ▁spark ▁advance ▁for ▁vehicles ▁experien cing ▁pre - ign ition ▁( k no ck ). ▁ ▁The ▁processor ▁module ▁featured ▁a ▁ 1 0 ▁volt ▁reference ▁for ▁its ▁analog - to - dig ital ▁converter ▁which ▁was ▁used ▁to ▁gather ▁data ▁from ▁various ▁sens ors . ▁ ▁This ▁could ▁have ▁been ▁an ▁issue ▁as ▁the ▁available ▁power ▁to ▁the ▁module ▁varied ▁above ▁and ▁below ▁ 1 0 ▁vol ts ▁during ▁engine ▁c ran king . ▁ ▁The ▁problem ▁was ▁solved ▁by ▁several ▁steps . ▁ ▁First , ▁all ▁sens ors ▁used ▁a ▁r ati ometric ▁meas uring ▁method ▁that ▁ins ured ▁accuracy ▁in ▁spite ▁of ▁varying ▁reference ▁voltage . ▁ ▁Second , ▁during ▁c ran king , ▁a ▁special ▁circuit ▁triggered ▁the ▁ign ition ▁system ▁in ▁synchron ization ▁with ▁the ▁reference ▁p uls es ▁from ▁the ▁engine . ▁ ▁Third , ▁the ▁processor ▁was ▁not ▁allowed ▁to ▁start ▁until ▁the ▁internal ▁voltage ▁was ▁stabil ized ▁above ▁ 1 0 ▁vol ts . ▁ ▁The ▁E EC - II ▁controlled ▁air - f uel ▁ratio ▁via ▁the ▁Ford ▁propriet ary