1999-2004 Honda TRX400EX FourTrax Service Manual, Page 231Get this manual
IGNITION SYSTEM
EXCITER COIL PEAK VOLTAGE
NOTE: Check that the cylinder compression is normal and the spark plug is installed correctly in the cylinder headDisconnect the ignition control module (ICM) connectorsConnect the peak voltage tester or adaptor probes to the connector terminals of the wire harness side
ICM CONNECTORS
CONNECTION:
Turn the ignition switch ONCrank the engine with the starter motor and read the peak voltage