Honda CBR125R Owner's Manual page 372

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 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 (and engine stop
switch " ": CM and U type) (The engine is not cranked by the starter motor).
No spark at spark plug
Unusual condition
Ignition coil No initial voltage with the ignition
primary volt- switch turned ON (and engine stop
age switch " ": CM and U type) (Other
electrical components are normal).
Initial voltage is normal, but it drops
by 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 the standard
value.
Initial and peak voltages are normal
but no spark jumps.
CKP sensor Peak voltage is lower than standard
value
No peak voltage
17-4
Probable cause (Check in numerical order)
1. Faulty ignition switch
2. An open circuit in Black/white wire between the igni-
tion coil and ignition switch
3. Loose or poor connection of the primary terminal, or
an open circuit in the primary coil
4. Faulty ECM (in case when the initial voltage is normal
with the ECM connector disconnected)
5. Faulty engine stop switch (CM and U type)
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 (+) wire and body
ground (–) at the ECM connector or loosen ECM con-
nection.
4. An open circuit or loose connection in Green wire at
the ECM.
5. An open circuit or loose connection in Pink/blue wire
between the ignition coils and ECM.
6. Faulty sidestand switch or neutral switch
7. Loose or poor connection or an open circuit in No. 6
related wires.
– Sidestand switch line: Green/white wire
– Neutral switch line: Light Green/red wire
8. Faulty CKP sensor (Measure peak voltage)
9. Faulty ECM (in case when above No. 1 through 8 are
normal)
1. Incorrect peak voltage adaptor connections.
2. Faulty peak voltage adaptor
3. Faulty CKP sensor
4. Faulty ECM (in case when above No. 1 through 3 are
normal).
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 ECM (in case when above No. 1 through 3 are
normal).
1. Faulty spark plug or leaking ignition coil secondary cur-
rent ampere
2. Faulty ignition coil
1. The multimeter impedance is too low; below 10 MΩ/
DCV.
2. Cranking speed is too low. (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 through 3
are normal).
1. Faulty peak voltage adapter
2. Faulty CKP sensor