Inspection Method Examples

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




- Continuity Check
- 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).





- Disconnect connector (B)and measure the resistance between connectors (A) and (B1), (B2) and (C).
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).




- Voltage Check
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.
- 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 5 V 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).


2. SHORT CIRCUIT CHECK




If the wire harness is ground shorted as in Fig. 5, locate the section by conducting a "continuity check with ground".
- Continuity Check with Ground
- Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connector (A) and body ground.





In the case of Fig. 6,
Between terminal 1 of connector (A) and body ground -> Continuity (short)
Between terminal 2 of connector (A) and body ground -> No Continuity
Therefore, it is found out that there is a short circuit between terminal 1 of connector (A) and terminal 1 of connector (C).





- Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body ground, and terminal 1 of connector (B2) and body ground.
Between terminal 1 of connector (A) and body ground -> No Continuity
Between terminal 1 of connector (B2) and body ground -> Continuity (short)
Therefore, it is found out that there is a short circuit between terminal 1 of connector (B2) and terminal 1 of connector (C).