How To Determine An Open Circuit

With voltmeter:
An open circuit is determined by measuring the voltage between respective connectors and ground using a voltmeter, starting with the connector closest to the power supply. The power supply must be turned ON so that current flows in the circuit. If voltage is not present between a particular connector and ground, the circuit between that connector and the previous connector is open.

Fig 1: Checking Open Circuit (With Voltmeter)
Courtesy of SUBARU OF AMERICA, INC.
With ohmmeter:
Disconnect all connectors affected, and check continuity in the wiring between adjacent connectors. When the ohmmeter indicates "infinite", the wiring is open.

Fig 2: Checking Open Circuit (With Ohmmeter)
Courtesy of SUBARU OF AMERICA, INC.