Possible causes for the open circuit are as follows. As the cause can exist in the connector/coupler or terminal, they need to be checked carefully.
When checking system circuits including an electronic control unit such as ecm, etc., It is important to perform careful check, starting with items which are easier to check.

|
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 fully inserted in the coupler and locked.
If contact tension is not enough, rectify the contact to increase tension or replace. The terminals must be clean and free of any foreign material which could impede proper terminal contact.

|
Locate abnormality, if any.

|
Battery
Continuity checkWater pump related parts inspection
Refer to “water pump disassembly and assembly” .
Mechanical seal
Visually inspect the mechanical seal for damage, with
particular attention given to the sealing face.
Replace the mechanical seal that shows indications of
leakage.
Oil seal
Visually inspect the oil seal for damage, with p ...
Ignition system check
Remove the spark plugs and
reattach them to the spark
plug caps.
Put the engine stop switch in
the "" position and ignition
switch in the "on" position.
While holding a spark plug
with its base firmly against the
engine, push the electric
starter butt ...
Continuity check
Measure resistance across coupler “b” (between “a”
and “c” in figure).
If no continuity is indicated (infinity or over limit), the
circuit is open between terminals “a” and “c”.
Disconnect the coupler “b” and measure resistance
between couplers “a” and “b-1”.
If no continuity ...