Honda NSS250S Manual page 159

PGM-FI SYMPTOM TROUBLESHOOTING
When the scooter has one of these symptoms, check the DTC or MIL blinking, refer to the DTC index (page 6-19) and begin
the appropriate troubleshooting procedure. If there are no DTC/MIL blinking stored in the PCM/ECM memory, do the diag-
nostic procedure for the symptom, in sequence listed below, until you find the cause.
Symptom
Engine cranks but won't
start
(No fuel pump operation
sound when turning the
ignition ON)
Engine cranks but won't
start
(No DTC and MIL blinking)
Engine stalls, hard to start,
rough idling
Afterburn when engine
braking is used
Backfiring or misfiring dur-
ing acceleration
Poor performance
(driveability) and poor fuel
economy
Idle speed is below specifi-
cations or fast idle too low
(No DTC and MIL blinking)
Idle speed is above specifi-
cations or fast idle too high
(No DTC and MIL blinking)
MIL never comes ON at all
MIL stays ON at all
(No DTC set)
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Diagnosis procedure
1. PCM/ECM power/ground cir-
cuits malfunction (page 6-67)
2. Inspect the fuel pump unit (page
6-76).
1. Inspect the IACV (page 6-103).
2. Inspect the ignition system
(page 20-5).
1. Inspect the idle speed (page 6-
102).
2. Inspect the IACV (page 6-103).
3. Inspect the fuel supply system
(page 6-71).
4. Inspect the ignition system
(page 20-5).
1. Inspect the PAIR system (page 6-
105).
2. Inspect the ignition system
(page 20-5).
Inspect the ignition system (page
20-5).
1. Inspect the fuel supply system
(page 6-71).
2. Inspect the ignition system
(page 20-5).
1. Inspect the idle speed (page 6-
102).
2. Inspect the IACV (page 6-103).
3. Inspect the fuel feed hose (page
6-71).
4. Inspect the ignition system
(page 20-5).
1. Inspect the idle speed (page 6-
102).
2. Inspect the throttle operation
and freeplay.
3. Inspect the IACV (page 6-103).
Inspect the MIL circuit (page 6-67).
Inspect the MIL/DLC circuits (page
6-67).
FUEL SYSTEM (PGM-FI)
Also check for
• Faulty bank angle sensor or related circuit
• Faulty engine stop relay or related circuit
• Faulty engine stop switch or related circuit
• Faulty ignition switch
• Faulty sensor unit or related circuit
• Faulty PCM/ECM
• Blown main fuse B (15 A)
• Blown ECU, IGN fuse (10 A)
• No fuel to injector
– Clogged fuel strainer screen
– Pinched or clogged fuel feed hose
– Pinched or clogged fuel filler cap
breather hole
– Faulty fuel pump unit or fuel pump unit
circuits
• Intake air leak
• Contaminated/deteriorated fuel
• Faulty sensor unit or related circuit
• Faulty fuel injector
• Restricted fuel feed hose
• Contaminated/deteriorated fuel
• Intake air leak
• Restricted fuel tank breather hose
• Pinched or clogged fuel feed hose
• Faulty pressure regulator in the fuel pump
unit
• Faulty injector
• Clogged air cleaner element
• Intake air leak
• Engine top end problem
• Air cleaner condition
6-5