Electrical Circuit Inspection Procedure
While there are various electrical circuit inspection
methods, described here is a general method to check
its open and short circuit by using an ohmmeter and a
Open Circuit Check
Possible causes for the open circuit are as follows. As
the cause is in the connector or terminal in many cases,
they need to be checked particularly carefully.
• Loose connection of connector
• Poor contact of terminal (due to dirt, corrosion or rust
on it, poor contact tension, entry of foreign object etc.)
• Wire harness being open
When checking system circuits including an electronic
control unit such as ECM, TCM, ABS / ESP® control
module, etc., it is important to perform careful check,
starting with items which are easier to check.
1) Disconnect negative (–) cable from battery
2) Check each connector at both ends of the circuit
being checked for loose connection. Also check lock
condition of connector if equipped with connector
3) Using a test male terminal, check both terminals of
the circuit being checked for contact tension of its
female terminal. Check each terminal visually for
poor contact (possibly caused by dirt, corrosion, rust
entry of foreign object, etc.). At the same time, check
to make sure that each terminal is locked in the
1. Check contact tension by inserting and removing just for once.
4) Using continuity check or voltage check the following
procedure, check the wire harness for open circuit
and poor connection with its terminals. Locate
abnormality, if any.
1) Measure resistance between connector terminals at
both ends of the circuit being checked (between "A-
1" and "C-1" in the figure). If no continuity is indicated
(infinity or over limit), that means that the circuit is
open between terminals "A-1" and "C-1".
2) Disconnect the connector included in the circuit
(connector-B in the figure) and measure resistance
between terminals "A-1" and "B-1".
If no continuity is indicated, that means that the
circuit is open between terminals "A-1" and "B-1". If
continuity is indicated, there is an open circuit
between terminals "B-1" and "C-1" or an abnormality
1. Looseness of crimping
3. Thin wire (single strand of wire)