How to distinguish the positive and negative electrodes of two rows of injectors

Color discrimination, voltage measurement discrimination.

1, color discrimination: the thick one is the positive line and the thick one is the negative line.

2. Difference of voltage measurement: set the multimeter to DC voltage range, and connect the probe in series to the signal line of the fuel injector. When the measured voltage is about 4.5 volts, the line measured with a red pen is a positive line, and the line measured with a black pen is a negative line.