Electrical Circuit Inspection Procedure: Notes

• Open Circuit Test

1. Procedures for Open Circuit
   • Continuity Check
   • Voltage Check

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

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2. Continuity Check Method
   NOTE: When measuring the resistance, lightly shake the wire harness vertically or horizontally.

   Specification (Resistance) 

   1Ω or less → Normal Circuit

   1MΩ or Higher → Open Circuit

   1. Disconnect connectors (A) and (C), and measure resistance between connectors (A) and (C) as shown in [Figure below].

      In [Figure below], if the measured resistances in lines 1 and 2 are "over 1 MΩ" and "below 1 Ω" respectively, line 1 has an open circuit. (Line 2 is normal.) To find the exact broken point, check the sub line of line 1 as described in the next step.

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   2. Disconnect connector (B), and measure the resistances between connectors (C) and (B1), and between (B2) and (A) as shown in [Figure below].

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

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

      The measured voltages of connectors are 5V, 5V and 0V respectively. So the open circuit is between connectors (C) and (B).

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