Sebastien Bourdais controlled proceedings all afternoon to take his second consecutive victory on the streets of San Jose and increase his championship lead back to more than 30 points.
The Frenchman led the majority of the 97 laps that made up the Canary Foundation Grand Prix and took the chequered flag nearly seven seconds clear of runner-up Cristiano da Matta.
Englishman Justin Wilson made up nine positions on his grid position to finish third and minimise the damage done by Bourdais in the chase for the title.
Nelson Philippe and Mario Dominguez completed the top five with leading rookie Will Power sixth and AJ Allmendinger seventh after a late race penalty for pitting when pit lane was closed.
Canadian duo Paul Tracy and Alex Tagliani crashed out of the race in controversial fashion on lap 52 when, as he recovered from an earlier spin, Tracy appeared to drive across the front of Tagliani's machine leading to a confrontation between the two in the pits.
British rookie and
Crash.Net columnist Katherine Legge finished 12th.
