Operation Instruction: 1.Turn off the vehicle's engine. 2.Connect the black clip to the negative terminal of the vehicle battery, connect the red clip to the positive terminal of the battery. 3.Locate the fuel injector which you want to test, then remove the electrical cable from this injector and connect the tester's two pulse output terminals to the electrical connector of this injector. 4. the MODE SET key to select the desired pulse mode, the display shows the current pulse mode. Injector Tester Specification: Power Supply:12V vehicle battery Operation Environment:0-40°C,relative humidity Less than 80% Storage Environment:-10°C ~50°C, relative humidity Less than 85% Test Cable Length: 41.5cm/ 16.3 inches Product Size:147x82x29mm Explanations for the 4 Modes: Mode1: the tester output 1 pulse, whose pulse width is about 250ms. Mode 2: the tester output 50 pulses, every pulse's pulse width is about 7ms. Mode 3: the tester output 100 pulses, every pulse's pulse width is about 3.5ms.