MerCruiser PCM-555 EFI
Page 42
Idle Air Control Output Test (non-DTS systems only)
The IAC Test allows the functionality of the engine’s Idle Air Control system
to be tested. This test commands the PCM module to change the IAC valve’s
position thereby changing the engine’s idle speed. Perform the following steps to
conduct the IAC test.
• IMPORTANT: This test should be performed in Neutral with the engine
idling and at normal operating temperature.
• Do not attempt to drive the boat while performing this test.
• Follow all engine and boat manufacturer’s safety precautions and stay
clear of all moving engine components.
1) Review the warnings stated above prior to conducting this test. For best
results the engine should be idling at normal operating temperature.
2) After selecting the “IAC Test“ function from the PCM Functions menu the
scanner will begin to display one or more advisory messages. Review these
messages and be certain their instructions are followed.
3) When the advisory messages have been displayed you may begin the test by
pressing the YES key. While the test is in progress the scanner will display
the current engine RPM as well as the IAC valve’s position. Use the
▲
and
▼
keys to change the IAC’s position in 5% increments. The IAC position range
is from -100% to +100%. While changing the IAC position you should hear a
noticeable change in engine speed.
4) To exit the IAC test press the NO key. You will be returned to the scanner’s
PCM Output Test menu.
Boost Valve Output Test (supercharged engines only)
This test allows a technician to check the functionality of the engine’s boost valve.
The test allows the boost valve duty cycle to be adjusted in 5 percent increments
using the scan tool’s
▲
and
▼
keys and also displays the current percent in
real-time.
• This test must be performed with Key-On, Engine Off
Follow the scan tool’s on screen prompts to proceed with the test.
• Press and hold the NO key on the scan tool’s keypad to stop the test
at any time.
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