Open circuit

GND circuit (No.1 cylinder fuel injector connector terminal B and PCM connector terminal 2A)
GND circuit (No.2 cylinder fuel injector connector terminal B and PCM connector terminal 2D)
GND circuit (No.3 cylinder fuel injector connector terminal B and PCM connector terminal 2G)

Fig 1: Identifying Main Relay Harness Side Connector
Courtesy of MAZDA MOTORS CORP.
GND circuit (No.4 cylinder fuel injector connector terminal B and PCM connector terminal 2J)
Power circuit (No.1 cylinder fuel injector connector terminal A and main relay connector terminal D through common connector)
Power circuit (No.2 cylinder fuel injector connector terminal A and main relay connector terminal D through common connector)
Power circuit (No.3 cylinder fuel injector connector terminal A and main relay connector terminal D through common connector)
Power circuit (No.4 cylinder fuel injector connector terminal A and main relay connector terminal D through common connector)