1999-2002 TRX400EX Fourtrax Service Manual, Page 229Get this manual
IGNITION SYSTEM
TROUBLESHOOTING
Inspect the following before diagnosing the system- Faulty spark plugLoose spark plug cap or spark plug wire connections -Water got into the spark plug cap (Leakingthe ignition coil secondary voltage) Ifthere is no spark at cylinder, temporarily exchange the ignition coil with good one and perform the spark testIfthere is spark, the exchanged ignition coil is faulty
No spark at spark plug UNUSUAL CONDITION gnition coil )rimary loltage Low peak voltage PROBABLE CAUSE (Check in numerical order) 1Incorrect peak voltage adaptor connections(System is normal if measured voltage is overthe specifications with reverse connections The multimeter impedance istoo low; 10 MOIDCV3Cranking speed istoo lowo Battery is undercharged4The sampling timing of the tester and measured pulse were not synchronized(System is normal if measured voltage is over the standard voltage at least once 5Poorly connected connectors or an open circuit in ignition system6Faulty exciter coil(Measure peakvoltage 7Faulty ignition coil8Faulty ignition control module (leM) (when above No.1 through are normal