2007-2011 Polaris IQ Snowmobiles Service Manual, Page 493Get this manual
Battery and Electrical Systems DETONATION CONTROL (DET)
Overview
Detonation control is achieved by using knock sensor mounted to the cylinder head and an ECU (CFI engines) or the CDI (600HO carbureted engines)The knock sensor "listens" for combustion knock by converting internal engine noise in to an electrical signalThe ECU or CDI uses the signal to determine the level of knock within the combustion chambers after each combustion eventWhen the ECU or CDI determines detonation has occurred, the CHECK ENGINEDET LED lamp will blink on and off at 0.5 second intervalsOn CFI models, the ECU will retard timing and provide additional fuel to eliminate the detonationOn carbureted engines, the CDI will retard timing until the detonation stopsIf the detonation continues past pre-determined level, the ECU or CDI will initiate an engine mis-fire modeTo prevent detonation, follow these steps: Always use premium fuel (91, 92, or 93 octane) On carbureted engines, follow the carburetor jetting guidelines Do not modify the engine or exhaust system with non-approved Polaris modifications Verify there is no water or foreign material in the fuel Verify there is no internal engine damage Verify the cooling system is working properly NOTE: Install the knock sensor fastener clean and dry without applying thread locker or oils