Examples of Circuit Inspections

OPEN CIRCUIT CHECKS

Fig. 1:

For the open circuit in the wire harness in Fig. 1, perform "CONTINUITY CHECK" or "VOLTAGE CHECK" to locate the section.

CONTINUITY CHECK
- Disconnect connectors (A) and (C) and measure the resistance between them.

Fig. 2:

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 (B), (B) and (C).

Fig. 3:

In the case of Fig. 3,
- Between terminal 1 of connector (A) and terminal 1 of connector (B) --> Continuity
- Between terminal 1 of connector (B) 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 (B) and terminal 1 of connector (C).

VOLTAGE CHECK
In a circuit in which voltage is applied (to the ECM connector terminal), an open circuit can be checked for by conducting a voltage check.

Fig. 4:

- As shown in Fig. 4, with each connector still connected, measure the voltage between body ground and terminal 1 of connector (A) at the ECM 5.0 volt output terminal, terminal 1 of connector (B), and terminal 1 of connector (C), in that order.
If the results are:
- Between Terminal 1 of connector (A) and Body Ground --> 5.0 volts
- Between Terminal 1 of connector (B) and Body Ground --> 5.0 volts
- Between Terminal 1 of connector (C) and Body Ground --> 0.0 volts
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).


SHORT CIRCUIT CHECKS

Fig. 5:

If the wire harness is ground shorted as in Fig. 5, locate the section by checking continuity with ground.

Fig. 6:

- 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
- Between terminal 2 of connector (A) and body ground --> No continuity (open)
Therefore, it is found out that there is a short circuit between terminal 1 of connector (A) and terminal 1 of connector (C).

Fig. 7:

- Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body ground, and terminal 1 of connector (B) and body ground.
In the case of Fig. 7.
- Between terminal 1 of connector (A) and body ground --> No continuity (open)
- Between terminal 1 of connector (B) and body ground --> Continuity
Therefore, it is found out that there is a short circuit between terminal 1 of connector (B) and terminal 1 of connector (C).