what does the icm do and what the systoms of its possible failure. my 1200c was running very rough at idle had it tunedup &rejetted now it idles real fast until you come to a stop then it slowly comes down to its normal idle. i have been told i now need a new icm doesnt make sense to me 2005 1200custom new plugs @oil@filter i did a diagnotic test (system code) there where no dtc codes but 32883-04 came up. this is the icm. what is the function of the icm and what are the visual or other signs of it going bad. this is an expensive item i would like to know more about the icm and its actual funtion cant get a decent reply from hd must be a big secret!!!!

 

Step #1 - What year is your bike??????????????????

That sounds like a bike with EFI which has an ECM

04-06 have an ICM
07 & up have an ECM

 

Tuned up?
What is a tune up?

On the newer bikes, that is replacing spark plugs as far as I know, as the timing is preset, there are no points, etc.

A rough idle can be worn out plugs, or wires, and in the carb models, carb problems (loose jets, float level off, dirt, vacuum leak).

The fuel injected models are like cars, they have idle speed control valves, the computer adjusts the idle speed automaticly, but there might be a learning process, or a vacuum leak could hose it up.
Fuel injected models also have diagnostics built in, which can tell you what is wrong.

Brett

 

ICM is the Ignition Control Module. It is actually a computer and controls numerous functions, from ignition timing to processing various sensor data including input from the MAP Sensor (manifold absolute pressure), Crank Position Sensor, to the Vehicle Speed sensor data that then drives your speedo, as well generating diagnostic failure information.

There is really no control circuit on a carbed Sporty that can hold the RPM at a high idle and then drop it off as you come to a stop. (Other than your right wrist) The carb is the source of vacuum for the bike, such as for operating the vacuum controlled petcock, but it is not a vacuum controlled device.


The 04-06 carbed, ICM equipped Sporty has the same diagnostic capability as the 07 EFI ECM equipped Sporty. In fact, they share the same diagnostic code list where applicable.

 

If its a carbed bike, the carbs are constant velocity I think, in which the slide is actually vacuum operated, and that might be sticking, throttle cable adjustment, etc.

Why add all those sensors and diagnostics on a carb bike?
Dit they have some sort of system that allowed the electronics to adjust the mixture?

Brett

 

Vacuum is generated by the intake stroke of the piston, which causes a suction (vacuum) through the carb throat. There is no vacuum operated "control" device on the carb. An increase in RPM (piston rate) increases suction through the carb, which then causes the slide to open further.


For better control of ignition timing, which means better controlled combustion under varying loads, which equals lower emissions.

 

As cHarley stated there is nothing to hold increased idle on a CV carb But for 2 things... binding cables (frayed or improperly adjusted) or the enrichener valve doing something weired.

But I would bet the Idle return cable is broken slowing the butterfly's return to idle position.

I dont think that the ICM could even hold the ignition timing high enough to cause a significant rise in idle.