2004 Official factory service manual for Yamaha YFZ450S ATV Quad., Page 332Get this manual
LIGHTING SYSTEM EBS01069
2Voltage Connect the pocket tester (AC 20 V) to the headlight couplers as shown When the light switch is set to "LO" When the light switch is set to "HI"
3Wiring Check the entire lighting system's wiringRefer to "CIRCUIT DIAGRAM" Is the lighting system's wiring properly connected and without defects? YES Check the condition of each of the lighting system's circuitsRefer to "CHECKING THE LIGHTING SYSTEM"EBS01070