Precautions: 00-4
• The ABS control unit/HU cannot be disassembled.
Replace the whole unit with a new one.
• Battery connection in reverse polarity is strictly
prohibited. Such a wrong connection will damage the
components of the ABS control unit/HU instantly when
reverse power is applied.
• Removing any battery terminal of a running engine is
strictly prohibited. The moment such removal is made,
damaging counter electromotive force will be applied
to the Ignition unit and ABS control unit/HU which may
result in serious damage.
• Before measuring voltage at each terminal, check to
make sure that battery voltage is 11 V or higher.
Terminal voltage check at low battery voltage will lead
to erroneous diagnosis.
• Never connect any tester (voltmeter, ohmmeter, or
whatever) to the Ignition and ABS control unit/HU
when its coupler is disconnected. Otherwise, damage
to Ignitor and ABS control unit/HU may result.
• Never connect an ohmmeter to the Ignitor and ABS
control unit/HU with its coupler connected. If
attempted, damage to Ignitor and ABS control unit/HU
or sensors may result.
• Be sure to use a specified voltmeter/ohmmeter.
Otherwise, accurate measurements may not be
obtained and personal injury may result.
Electrical Circuit Inspection Procedure
While there are various methods for electrical circuit
inspection, described here is a general method to check
for open and short circuit using an ohmmeter and a
voltmeter.
Open circuit check
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.
• Loose connection of connector/coupler
• Poor contact of terminal (due to dirt, corrosion or rust,
poor contact tension, entry of foreign object etc.)
• Wire harness being open.
• Poor terminal-to-wire connection.
When checking system circuits including an electronic
control unit such as ignitor, ABS control unit/HU, etc., it is
important to perform careful check, starting with items
which are easier to check.
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