So I am having an issue with my 06 496 Mag HO and many have suggested it might be an IAC. I put the software on and ran the IAC test but never doing this before I want to make sure. I followed the instructions and warmed up the engine, in neutral and with the software running. I started the test and it asked me to raise and lower by hitting the arrows. I did each way, all the way and nothing changed. It said the idle should change as I change in the test but for me nothing changed at all, it stayed completely the same. So I am assuming I would notice the change and this means the IAC is actually bad or did I mess up the test?

Before you condemn iac ,pull out the iac muffler and make the same test ....The diacom software should change iac setting(which will change idle speed).....Probably is a bad iac ,but a lot of iac mufflers are stopped up.

so thats how the test is supposed to work? Muffler? where is that sounds like your pulling a headlight fluid joke on me.

# 5 on diagram
http://www.mercruiserparts.com/Show_...le%2DShift+%29

Run your motor with diacom running.

Go to the graph tab.

Select IAC level as one of the parameters.

While idling, the IAC level should look like a heartbeat line. If it's a flat line, the IAC is bad.

I found the problem, it was a pressure sendor which Diacom had as a fault. I assume my IAC is good but according to the software it was not. I am still confused on the IAC test since my idle never changed during the test multiple times. I could see under live data that it was changing. It is fixed though!