Electrical Circuit Inspection Procedure

Check Open Circuit

Procedures for Open Circuit

Continuity Check
Voltage Check

If an open circuit occurs (as seen in Figure below), it can be found by performing Step 2 (Continuity Check Method) or Step 3 (Voltage Check Method) as shown below.

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Continuity Check Method

NOTE:

When measuring for resistance, lightly shake the wire harness above and below or from side to side.

Specification (Resistance)

1Ωor less → Normal Circuit

1MΩor Higher → Open Circuit

Disconnect connectors (A), (C) and measure resistance between connector (A) and (C) as shown in Fig 1.
In Fig 1 the measured resistance of line 1 and 2 is higher than 1MΩand below 1Ωrespectively. Specifically the open circuit is line 1 (Line 2 is normal). To find exact break point, check sub line of line 1 as described in next step.

Fig 1: Measuring Resistance
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Disconnect connector (B), and measure for resistance between connector (C) and (B1) and between (B2) and (A) as shown in Figure below.

In this case the measured resistance between connector (C) and (B1) is higher than 1MΩand the open circuit is between terminal 1 of connector (C) and terminal 1 of connector (B1).

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Voltage Check Method

With each connector still connected, measure the voltage between the chassis ground and terminal 1 of each connectors (A), (B) and (C) as shown in Figure below .

The measured voltage of each connector is 5V, 5V and 0V respectively. So the open circuit is between connector (C) and (B).

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Check Short Circuit

Test Method for Short to Ground Circuit

Continuity Check with Chassis Ground

If short to ground circuit occurs as shown in Figure below, the broken point can be found by performing Step 2 (Continuity Check Method with Chassis Ground) as shown below.

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Continuity Check Method (with Chassis Ground)

NOTE:

Lightly shake the wire harness above and below, or from side to side when measuring the resistance.

Specification (Resistance)

1Ωor less → Short to Ground Circuit

1MΩor Higher → Normal Circuit

Disconnect connectors (A), (C) and measure for resistance between connector (A) and Chassis Ground as shown in Figure below.

The measured resistance of line 1 and 2 in this example is below 1Ωand higher than 1MΩrespectively. Specifically the short to ground circuit is line 1 (Line 2 is normal). To find exact broken point, check the sub line of line 1 as described in the following step.

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Disconnect connector (B), and measure the resistance between connector (A) and chassis ground, and between (B1) and chassis ground as shown in Figure below.

The measured resistance between connector (B1) and chassis ground is 1Ωor less. The short to ground circuit is between terminal 1 of connector (C) and terminal 1 of connector (B1).

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