The Dane eclipsed early pacesetter Lewis Hamilton's Mercedes by two tenths of a second, with Force India's Nico Hulkenberg completing a Mercedes-engined lockout of the top three places on the timesheet.
The Lotus E22 made its public debut, completing seven laps in the hands of Romain Grosjean.
The Frenchman was outpaced by Robin Frijns, who set the sixth fastest time for Caterham and completed 26 laps.
The problems continued at fellow Renault-powered outfits Red Bull and Toro Rosso, as neither squad completed any running in the morning.
Red Bull kept its RB10 out of sight behind garage doors as the team worked to get it running without success.
The Toro Rosso suffered an oil leak, so new signing Daniel Kvyat has yet to complete a lap.
Ferrari's Fernando Alonso caused the first red flag of the day when the Ferrari F14 T first left the pits billowing smoke thanks to an oil leak.
Alonso went on to set the fourth fastest time, 1.1s clear of Sauber's Adrian Sutil, who brought out the red flags again after spinning at Turn 1.
Felipe Massa's Williams and Jules Bianchi's Marussia only completed a handful of installation laps at the start of the test, which was delayed by 30 minutes due to confusion over the number of marshals present at the circuit.
Follow the Bahrain test as it happens with AUTOSPORT Live.
- Motor Racing
- Toro Rosso
- Lewis Hamilton
- Robin Frijns
- Nico Hulkenberg