Check open circuit - Introduction - Toyota Supra A80

For the open circuit in the wire harness in Fig. 1, perform ”(a) Continuity Check” or ”(b) Voltage Check” to locate the section.

1. Check the continuity.
   1. Disconnect connectors (A) and (C) and measure the resistance between them.
      In the case of Fig. 2,
      Between terminal 1 of connector (A) and terminal 1 of connector (C) → No continuity (open)
      Between terminal 2 of connector (A) and terminal 2 of connector (C) → Continuity
      Therefore, it is found out that there is an open circuit between terminal 1 of connector (A) and terminal 1 of connector (C).
   2. Disconnect connector ”B” and measure the resistance between the connectors.
      In the case of Fig.3,
      Between terminal 1 of connector ”A” and terminal 1 of connector ”B1” → Continuity
      Between terminal 1 of connector ”B2” and terminal 1 of connector ”C” → No continuity (open)
      Therefore, it is found out that there is an open circuit between terminal 1 of connector ”B2” and terminal 1 of connector ”C”.
   
2. Check the voltage.
   In a circuit in which voltage is applied (to the ECU connector terminal), an open circuit can be checked for by conducting a voltage check.
   1. As shown in Fig. 4, with each connector still connected, measure the voltage between body ground and terminal 1 of connector (A) at the ECU 5V output terminal, terminal 1 of connector (B), and terminal 1 of connector (C), in that order.
      If the results are:
      5 V: Between Terminal 1 of connector (A) and Body Ground
      5 V: Between Terminal 1 of connector (B) and Body Ground
      0 V: Between Terminal 1 of connector (C) and Body Ground
      then it is found out that there is an open circuit in the wire harness between terminal 1 of (B) and terminal 1 of (C).