2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 358Get this manual
2WD4WD SELECTING SYSTEM EB803020
TROUBLESHOOTING IF THE FOUR-WHEEL DRIVE INDICATOR LIGHT FAILS TO COME ON: Procedure Check: 1.Fuse (main, four-wheel drive) 2.Battery 3.Main switch 4.On command four-wheel drive switch NOTE: Remove the following part(s) before troubleshooting: 1)Seat 2)Front carrier 3)Front fender Use the following special tool(s) for troubleshooting
5.Gear motor 6.Wiring connections (the entire 2WD4WD selecting system)
Pocket tester: PNYU-03112, 90890-03112