Testing began at 10am and concludes at 6pm.
The session was briefly red flagged to allow some work on the trackside electronics, while most riders are at lunch. Yamaha riders Ben Spies and Jorge Lorenzo have both fallen, but were unhurt.
Honda riders Casey Stoner, Dani Pedrosa, Alvaro Bautista and Stefan Bradl are returning to action after missing day two while HRC carried out engine checks following a problem on Pedrosa's bike.
Karel Abraham (Cardion AB Ducati) withdrew from the test on day one due to pain from shoulder and back injuries sustained at Jerez last week.
The first two days of testing were both interrupted by rain storms.
The third and final official pre-season test will be held at Jerez from March 23-25, when the full 21-rider grid - twelve manufacturer bikes plus nine CRTs - will be on track together for the first time.CLICK HERE
for pictures from the second Sepang test...
1. Casey Stoner
AUS Repsol Honda 2m 0.473s
2. Jorge Lorenzo
ESP Yamaha Factory Racing 2m 0.877s
3. Dani Pedrosa
ESP Repsol Honda 2m 1.115s
4. Andrea Dovizioso
ITA Monster Yamaha Tech 3 2m 1.315s
5. Ben Spies
USA Yamaha Factory Racing 2m 1.432s
6. Cal Crutchlow
GBR Monster Yamaha Tech 3 2m 1.454s
7. Valentino Rossi
ITA Ducati Team 2m 1.550s
8. Nicky Hayden
USA Ducati Team 2m 1.609s
9. Hector Barbera
ESP Pramac Racing 2m 1.623s
10. Alvaro Bautista
ESP San Carlo Honda Gresini 2m 1.640s
11. Stefan Bradl
GER LCR Honda 2m 1.900s
12. Franco Battaini
ITA Ducati Test Rider 2m 3.490s
13. Colin Edwards
USA Forward Racing (Suter-BMW CRT) 2m 5.152s
14. Ivan Silva
ESP Avintia (FTR-Kawasaki CRT) 2m 7.228s
15. Yonny Hernández
COL Avintia (FTR-Kawasaki CRT) 2m 7.278s
(14/22)Fastest day two time:Ben Spies
USA Yamaha 2m 1.285sFastest day one time:Casey Stoner
AUS Honda 2m 1.761sFastest Sepang I test times (Feb 2):By manufacturer:Casey Stoner
AUS Honda 1m 59.607sJorge Lorenzo
ESP Yamaha 2m 0.198sValentino Rossi
ITA Ducati 2m 0.824sColin Edwards
USA Suter 2m 4.722sIvan Silva
ESP FTR 2m 8.225sOfficial Sepang MotoGP lap records:Pole position: Valentino Rossi
ITA Yamaha 2m 0.518s
(2009)Fastest race lap:Casey Stoner
AUS Ducati 2m 2.108s