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.

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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.

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Locate abnormality, if any.

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Battery
Continuity checkIgnition coil and spark plug removal and
installation
Removal
The hot
engine can burn you.
Wait until the engine is cool enough to touch.
Turn the ignition switch off.
Remove the air cleaner box. Refer to “air cleaner box removal and
installation” in section 1d .
Disconnect the lead wire couplers (1).
...
Crankshaft journal bearing inspection and
selection
Refer to “engine bottom side disassembly” (page 1d-
49).
Refer to “engine bottom side assembly” .
Inspection
Inspect each upper and lower crankcase bearing for
any damage.
Set the crankshaft onto the upper crank case.
Install the plastigauge onto each crankshaft jour ...
Ckp sensor inspection
Refer to “electrical components location” in section 0a .
Ckp sensor peak voltage
Lift and support the fuel tank. Refer to “fuel tank
removal and installation” in section 1g (page 1g-
9).
Disconnect the ckp sensor coupler (1).
Note
be sure that all of the couplers are connect ...