Service manual

G420F(FE) Service Manual 253 Chapter 8. Basic Troubleshooting
Electrical Circuit Inspection Procedure
● Check Open Circuit
1. Procedures for Open Circuit
• Continuity Check
• Voltage Check
If an open circuit occurs (as seen in [FIG.1]), it can
be found by performing Step 2 (Continuity Check) or
Step 3 (Voltage Check Method) as shown below.
2. Continuity Check Method
NOTE: When measuring for resistance, lightly shake
the wire harness above and below or from side to
side.
Specification (Resistance)
1Ω or less → Normal Circuit
1㏁ or Higher → Open Circuit
a. Disconnect connectors (A), (C) and measure
resistance between connector (A) and (C) as
shown in [FIG.2].
In [FIG.2.] the measured resistance of line1and
2 is higher than 1㏁ and below 1Ω respectively.
Specifically the open circuit is line 1(Line 2 is
normal). To find exact break point, check sub line of
line 1as described in next step.
b. Disconnect connector (B), and measure for
resis tance between connector (C) and (B1)
and between (B2) and (A) as shown in [FIG.3].
In this case the measured resistance between
connector (C) and (B1) is higher than 1㏁ and
the open circuit is between terminal 1 of
connector (C) and terminal 1 of connector (B1).
3. Voltage Check Method
a. With each connector still connected, measure
the voltage between the chassis ground and
terminal1 of each connectors (A), (B) and (C)
as shown in [FIG.4].
The measured voltage of each connector is 5V,
5V and 0V respectively. So the open circuit is
between connector (C) and (B).