A large quantity of dust was brought onto the track by drivers dropping wheels off the track, and Lukoil SEAT driver Tarquini received a black and white warning flag for repeatedly cutting Turn 3A early in the session.
Ex-Formula 1 driver Tiago Monteiro's SUNRED machine ended the session in third, ahead of Tom Boardman.
Briton Boardman was the first man into the 1m46s in the session to briefly top the timing screens shortly after the midway point.
After a puncture disrupted his acclimatisation to Sonoma on Friday, Rob Huff was markedly closer to the top of the classification in FP2 and claimed fifth place.
The third RML-prepared factory Chevrolet of Alain Menu completed the top six.
Tarquini's team-mate Aleksei Dudukalo was seventh ahead of 2012 European Touring Car Cup winner Fernando Monje. Both men enjoyed spells at the top of the classification.
Several BMW runners suffered multiple spins. Stefano D'Aste appeared to encounter great difficulty negotiating Turn 2 without drama in his Wiechers-Sport entry, and Franz Engstler also pirouetted.
After an awkward inter-team collision in FP1, ROAL Motorsport team-mates Tom Coronel and Alberto Cerqui confined their dramas to individual moments.
Pos Driver Team/Car Time Gap 1. Gabriele Tarquini Lukoil SEAT 1m46.457s 2. Yvan Muller Chevrolet 1m46.743s + 0.286s 3. Tiago Monteiro SUNRED SEAT 1m46.881s + 0.424s 4. Tom Boardman Special Tuning SEAT 1m46.885s + 0.428s 5. Robert Huff Chevrolet 1m46.987s + 0.530s 6. Alain Menu Chevrolet 1m47.080s + 0.623s 7. Aleksei Dudukalo Lukoil SEAT 1m47.136s + 0.679s 8. Fernando Monje SUNRED SEAT 1m47.224s + 0.767s 9. James Nash Arena Ford 1m47.308s + 0.851s 10. Tom Chilton Arena Ford 1m47.369s + 0.912s 11. Darryl O'Young Special Tuning SEAT 1m47.493s + 1.036s 12. Norbert Michelisz Zengo BMW 1m47.495s + 1.038s 13. Pepe Oriola Tuenti SEAT 1m47.593s + 1.136s 14. Franz Engstler Engstler BMW 1m47.828s + 1.371s 15. Tom Coronel ROAL BMW 1m48.089s + 1.632s 16. Alberto Cerqui ROAL BMW 1m48.471s + 2.014s 17. Alex MacDowall Bamboo Chevrolet 1m48.592s + 2.135s 18. Mehdi Bennani Proteam BMW 1m48.674s + 2.217s 19. Charles Ng Engstler BMW 1m48.967s + 2.510s 20. Stefano D'Aste Wiechers BMW 1m48.972s + 2.515s 21. Robb Holland Bamboo Chevrolet 1m49.712s + 3.255s
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