Fenninger, who missed out in Meribel last week with an illness, returned strongly with the leading time, ahead of German hope Maria Riesch-Hoefl by just 0.03 of a second.
Norway's Lotte Smiseth Sejersted took third place in the first warm-up, while Tina Maze found herself down in 13th, over a second and a half off the pace.
The downhill takes place on the German border on March 1.
1st Anna Fenninger AUT 1:41,99
2nd Maria Riesch-Hoefl GER + 0,03
3rd Lotte Smiseth Sejersted NOR 0.36
4th Regina mush AUT 0.44
5th Julia Mancuso USA 0.55
6th Carolina Ruiz Castillo ESP 0.62
7th Marie Marchand-Arvier FRA 0.63
8th Lara Gut SUI 0.92
9th Daniela Merighetti ITA 1.18
10th Ilka Stuhec SLO 1.24