4-4 FI SYSTEM AND INTAKE AIR SYSTEM
• Removing any battery terminal of a running engine is strictly
prohibited.
The moment such removal is made, damaging counter electro-
motive force will be applied to the ECM which may result in
serious damage.
• Before measuring voltage at each terminal, check to make
sure that battery voltage is 11V or higher. Terminal voltage
check at low battery voltage will lead to erroneous diagnosis.
• Never connect any tester (voltmeter, ohmmeter, or whatever)
to the ECM when its coupler is disconnected. Otherwise, dam-
age to ECM may result.
• Never connect an ohmmeter to the ECM with its coupler con-
nected. If attempted, damage to ECM or sensors may result.
• Be sure to use a specified voltmeter/ohmmeter. Otherwise, ac-
curate 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
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