I have Pacific 1940 2nd ed. game that I bought in May '13 or thereabouts. Convoy rules are on pp. 22-23. They read like the Europe/L.Harris rules that Gargantua has cited: units roll dice, 2 for a/c and subs, and 1 for others. Rolls of “3” or less are tallied, etc. Exactly like my Europe '40 2nd ed. rulebook in game I purchased the same day.
The Pac. '40 2nd ed. rulebook in A&A.org / Resources section is like the one that came with my game.
I did look at Avalon Hill site for Pac. '40 2nd ed. rulebook and it reads the way that Gargantua is citing for Pacific rules, units do an amount of convoy ipc damage without rolling dice. Looked again at cover of that book, however, and it does not indicate “2nd Edition”. Seems like a bad link at AH site. Rulebook link on Pacific '40 2nd ed. page opens 1st ed. book?
Also confirmed that my Pacific rulebook on pg. 10 says that China is not subject to convoy disruption, as P@nther previously noted.