Honda NSS250S Manual page 546

IGNITION SYSTEM
TROUBLESHOOTING
• Inspect the following before diagnosing the system.
– Faulty spark plug
– Loose spark plug cap or spark plug wire connection
– Water got into the spark plug cap (leaking the ignition coil secondary voltage)
• If there is no spark at the cylinder, temporarily exchange the ignition coil with a known good one and perform the spark
test. If there is spark, the original ignition coil is faulty.
• "Initial voltage" of the ignition primary coil is the battery voltage with the ignition switch turned ON (The engine is not
cranked by the starter motor).
NO SPARK AT PLUG
Unusual condition
Ignition coil No initial voltage with engine stop
primary volt- switch turned " " and ignition
age switch turned ON (Other electrical
components are normal).
Initial voltage is normal, but it drops
down to 2 – 4 V while cranking the
engine.
Initial voltage is normal, but there is
no peak voltage while cranking the
engine.
Initial voltage is normal, but peak
voltage is lower than standard value.
Initial and peak voltage are normal,
but does not spark.
CKP sensor Peak voltage is lower than standard
value.
No peak voltage.
20-4
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Probable cause (Check in numerical order)
1. Faulty engine stop switch
2. An open circuit or loose connection in engine stop
relay related circuit or faulty engine stop relay
3. Loose or poor contact of the ignition coil primary wire
terminal, or an open circuit in primary coil.
4. Faulty PCM/ECM (in case when the initial voltage is
normal while disconnecting PCM/ECM connector)
1. Incorrect peak voltage adaptor connections (System is
normal if measured voltage is over the specifications
with reverse connections).
2. Battery is undercharged (Voltage drops largely when
the engine is started).
3. No voltage between the Black/white (+) and body
ground (–) at the PCM/ECM connector or loosen PCM/
ECM connection.
4. An open circuit or loose connection in Green wire of
the PCM/ECM.
5. An open circuit or loose connection in Yellow/blue
wire between the ignition coil and PCM/ECM.
6. Short circuit in Black/white wire of the ignition coil.
7. Faulty sidestand switch
8. An open circuit or loose connection in sidestand
switch related circuit.
9. Faulty CKP sensor (measure the peak voltage)
10.Faulty PCM/ECM (in case when above No.1 - 9 are nor-
mal)
1. Incorrect peak voltage adaptor connections (System is
normal if measured voltage is over the specifications
with reverse connections).
2. Faulty peak voltage adaptor
3. Faulty CKP sensor
4. Faulty PCM/ECM (in case when above No.1, 2 are nor-
mal)
1. The multimeter impedance is too low; below 10 MΩ/
DCV.
2. Cranking speed is too slow (Battery is undercharged).
3. The 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).
4. Faulty PCM/ECM (in case when above No.1 – 3 are nor-
mal)
1. Faulty spark plug or leaking ignition coil secondary
current ampere
2. Faulty ignition coil.
1. The multimeter impedance is too low; below 10 MΩ/
DCV.
2. Cranking speed is too slow (Battery is undercharged).
3. The 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).
4. Faulty CKP sensor (in case when above No. 1 – 3 are
normal)
1. Faulty peak voltage adaptor
2. Faulty CKP sensor