2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 507Get this manual
LIGHTSSWITCHES (After '05) Ground the ECT sensor connector with jumper wireStart the engine and check the indicator If the indicator lights, the system is OK If the indicator does not light or lights for seconds then goes off, check for an open circuit in the following wire:Yellowblue wire between the ECT sensor and fanICM connectorsGray wire between the fanICM and indicator connectors
If the wire is OK, disconnect the indicator 4P natural (TRX450ER) or 2P red (TRX450R) connectorStart the engine and measure the voltage between the Black wire terminal (+) and Gray wire terminal (-) of the wire harness side connector If there is generating voltage, check for blown indicator bulb If there is no voltage, check for an open circuit in the black wire between the indicator and ignition switch connectorsIf the black wire is OK, replace the fanICMINDICATOR 4P(TRX450ER) or 2P (TRX450R) CONNECTOR