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 checkDrive chain related parts inspection
Refer to “rear sprocket / rear sprocket mounting drum removal and
installation” .
Dust seal
Inspect the dust seal for wear or damage. If any damage
is found, replace the dust seal with a new one.
Bearing
Inspect the play of the sprocket mounting drum bearing
by hand while it is in the dr ...
Clutch cable play inspection and adjustment
Inspect clutch cable play
every 6 000 km (4 000 miles, 12 months)
Inspect and adjust the clutch cable play “a” as follows.
Clutch cable play “a”
10 – 15 mm (0.4 – 0.6 In)
Lift and support the fuel tank. Refer to “fuel tank
removal and installation” in section 1g (page 1g-
9).
  ...
Valve clearance inspection and adjustment
Inspect valve clearance
initially every 24 000 km (14 500 miles, 48 months)
Inspection
Valve clearance adjustment must be checked and
adjusted, a) at the time of periodic inspection, b) when
the valve mechanism is serviced, and c) when the
camshafts are removed for servicing.
Lift an ...