rider about the conditions [B] of trouble, and then start to
determine the cause [C] of problem.
As a pre-diagnosis inspection, check the ECU for ground
and power supply, the fuel line for no fuel leaks, and for
correct pressure. The pre-diagnosis items are not indicated
by the yellow engine warning indicator light (LED).
Do not rely solely on the DFI self-diagnosis function, use
common sense.
Even when the DFI system is operating normally, the yellow engine warning indicator light (LED) goes on may be
displayed under strong electrical interference. Additional
measures are not required. Turn the ignition switch off to
stop the indicator.
If the yellow engine warning indicator light (LED) of the
motorcycle brought in for repair still goes on, check the service code.
When the repair has been done, the yellow engine
warning indicator light (LED) goes off after the service
code erasing procedure (see Service Code Erasing in the
Self-Diagnosis System chapter) is done.
When the motorcycle is down, the vehicle-down sensor
operates and the ECU shuts off the fuel pump relay, fuel
injectors and ignition system. The ignition switch is left on.
If the starter button is pushed, the electric starter turns but
the engine does not start. To start the engine again, raise
the motorcycle, turn the ignition switch off, and then on.
Much of the DFI system troubleshooting work consists
of confirming continuity of the wiring. The DFI parts are
assembled and adjusted with precision, and it is impossible
to disassemble or repair them.

FUEL SYSTEM (DFI) 3-29
Troubleshooting the DFI System
checking the DFI parts, use a digital meter which
• When
can be read two decimal place voltage or resistance.

○The DFI part connectors [A] have seals [B], including the

ECU. When measuring the input or output voltage with the
connector joined, use the needle adapter set [C]. Insert
the needle adapter inside the seal until the needle adapter
reaches the terminal.
Special Tool - Needle Adapter Set: 57001-1457

NOTICE
Insert the needle adapter straight along the terminal
in the connector to prevent short-circuit between
terminals.
sure that measuring points are correct in the con• Make
nector, noting the position of the lock [D] and the lead

•
•

color before measurement. Do not reverse connections
of a digital meter.
Be careful not to short-circuit the leads of the DFI or electrical system parts by contact between adapters.
Turn the ignition switch on and measure the voltage with
the connector joined.

NOTICE
Incorrect, reverse connection or short circuit by
needle adapters could damage the DFI or electrical
system parts.

○After measurement, remove the needle adapters and apply silicone sealant to the seals [A] of the connector [B]
for waterproofing.
Sealant - Liquid Gasket, TB1211: 56019-120

check battery condition before replacing the DFI
• Always
parts. A fully charged battery is a must for conducting

•
•
•

accurate tests of the DFI system.
Trouble may involve one or in some cases all items.
Never replace a defective part without determining what
CAUSED the problem. If the problem was caused by
some other item or items, they too must be repaired or
replaced, or the new replacement part will soon fail again.
Measure the coil winding resistance when the DFI part is
cold (at room temperature).
Make sure all connectors in the circuit are clean and tight,
and examine wires for signs of burning, fraying, short,
etc. Deteriorated leads and bad connections can cause
reappearance of problems and unstable operation of the
DFI system.
If any wiring is deteriorated, replace the wiring.

3-30 FUEL SYSTEM (DFI)
Troubleshooting the DFI System
each connector [A] apart and inspect it for corrosion,
• Pull
dirt, and damage.
If the connector is corroded or dirty, clean it carefully. If it
is damaged, replace it. Connect the connectors securely.
Check the wiring for continuity.
○Use the wiring diagram to find the ends of the lead which
is suspected of being a problem.
○Connect a tester between the ends of the leads.
If the tester does not read about 0 Ω, the lead is defective.
Replace the lead or the main harness or the subharness.

•

○If both ends of a harness [A] are far apart, ground [B] the
one end [C], using a jumper lead [D] and check the continuity between the end [E] and the ground [F]. This enables to check a long harness for continuity. If the harness
is open, repair or replace the harness.

○When checking a harness [A] for short circuit, open one
end [B] and check the continuity between the other end
[C] and ground [D]. If there is continuity, the harness has
a short circuit to ground, and it must be repaired or replaced.

down suspicious locations by repeating the con• Narrow
tinuity tests from the ECU connectors.
If no abnormality is found in the wiring or connectors, the
DFI parts are the next likely suspects. Check the part,
starting with input and output voltages. However, there is
no way to check the ECU itself.
If an abnormality is found, replace the affected DFI part.
If no abnormality is found in the wiring, connectors, and
DFI parts, replace the ECU.

FUEL SYSTEM (DFI) 3-31
Troubleshooting the DFI System
DFI Diagnosis Flow Chart

Inquiries to Rider

○Each rider reacts to problems in different ways, so it is important to confirm what kind of symptoms
the rider has encountered.

○Try to find out exactly what problem occurred under exactly what conditions by asking the rider;
knowing this information may help you reproduce the problem.
○The following sample diagnosis sheet will help prevent you from overlooking any areas, and will
help you decide if it is a DFI system problem, or a general engine problem.

3-32 FUEL SYSTEM (DFI)
Troubleshooting the DFI System
Sample Diagnosis Sheet
Rider name: Registration No. (license plate No.):
Year of initial registration:
Model:
Engine No.:
Frame No.:
Date problem occurred:
Mileage:
Environment when problem occurred.
Weather
□ fine, □ cloudy, □ rain, □ snow, □ always, □ other:
Temperature □ hot, □ warm, □ cold, □ very cold, □ always, □ other:
Problem
□ chronic, □ often, □once
frequency
Road
□ street, □ highway, □ mountain road (□ uphill, □ downhill), □ bumpy, □ pebble
Altitude
□ normal, □ high (about 1 000 m or more)
Motorcycle conditions when problem occurred.
Yellow engine □ goes on immediately after turning the ignition switch on, and goes off after about
1 second (normal)
warning
indicator light □ goes on immediately after turning the ignition switch on, goes off after about 1
(LED)
second, and goes on again after about 5 seconds (ECU communication error)
□ goes on immediately after turning the ignition switch on, goes off after about 1
second, and goes on again and stays on (DFI problem)
□ does not go on after turning the ignition switch on [indicator light (LED), meter
unit fault]
Red warning □ Starts blinking about 2 seconds after ignition switch on (immobilizer system
indicator light
problem).
(LED)
□ Does not go on about 2 seconds after ignition switch on (ECU or meter unit fault).
□ Light up (battery, oil pressure, water temperature or meter unit problem)
Starting
□ starter motor not rotating.
difficulty
□ starter motor rotating but engine do not turn over.
□ starter motor and engine do not turn over.
□ no fuel flow (□ no fuel in tank, □ no fuel pump sound).
□ no spark.
□ other:
Engine stalls □ right after starting.
□ when opening throttle grip.
□ when closing throttle grip.
□ when moving off.
□ when stopping the motorcycle.
□ when cruising.
□ other:

FUEL SYSTEM (DFI) 3-33
Troubleshooting the DFI System
Poor running
at low speed

Poor running
or no power at
high speed

□ very low idle speed, □ very high idle speed, □ rough idle speed.
□ battery voltage is low (charge the battery).
□ spark plug loose (tighten it).
□ spark plug dirty, broken, or gap maladjusted (remedy it).
□ backfiring.
□ afterfiring.
□ hesitation when acceleration.
□ engine oil viscosity too high.
□ brake dragging.
□ engine overheating.
□ clutch slipping.
□ other:
□ spark plug loose (tighten it).
□ spark plug dirty, broken, or gap maladjusted (remedy it).
□ spark plug incorrect (replace it).
□ knocking (fuel poor quality or incorrect, → use high-octane gasoline).
□ brake dragging.
□ clutch slipping.
□ engine overheating.
□ engine oil level too high.
□ engine oil viscosity too high.
□ other:

3-34 FUEL SYSTEM (DFI)
DFI System Troubleshooting Guide
NOTE

○This is not an exhaustive list, giving every possible cause for each problem listed. It is meant
simply as a rough guide to assist the troubleshooting for some of the more common difficulties in
DFI system.
○The ECU may be involved in the DFI electrical and ignition system troubles. If these parts and
circuits are checked out good, be sure to check the ECU for ground and power supply. If the
ground and power supply are checked good, replace the ECU.
Engine Won’t Turn Over
Symptoms or Possible Causes
Gear position sensor, starter lockout or side
stand switch trouble
Immobilizer system trouble
Vehicle-down sensor operated
Vehicle-down sensor trouble
Crankshaft sensor trouble
Stick coil shorted or not in good contact
Stick coil trouble
Spark plug dirty, broken or gap maladjusted
Spark plug incorrect
ECU ground and power supply trouble
ECU trouble
No or little fuel in tank
Fuel injector trouble
Fuel pump not operating
Fuel pump relay trouble
Fuel filter or pump screen clogged
Fuel pressure regulator trouble
Fuel line clogged

Actions (chapter)
Inspect each switch and sensor (see chapter 16).
Inspect (see chapter 17).
Turn ignition switch off (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 16).
Inspect or reinstall (see chapter 16).
Inspect (see chapter 16).
Inspect and replace (see chapter 2).
Replace it with correct plug (see chapter 2).
Inspect (see chapter 3).
Inspect (see chapter 3).
Supply fuel (see Owner’s Manual).
Inspect and replace (see chapter 3).
Inspect (see chapter 3).
Inspect and replace (see chapter 3).
Inspect and replace fuel filter or fuel pump (see
chapter 3).
Inspect fuel pressure and replace fuel pump (see
chapter 3).
Inspect and repair (see chapter 3).

Poor Running at Low Speed
Symptoms or Possible Causes
Spark weak:
Stick coil shorted or not in good contact
Stick coil trouble
Spark plug dirty, broken or gap maladjusted
Spark plug incorrect
ECU trouble
Fuel/air mixture incorrect:
Little fuel in tank
Air cleaner clogged, poorly sealed, or missing
Air intake duct loose
Throttle body assy holder loose
Throttle body assy O-ring damage
Fuel injector O-ring damage

Actions (chapter)
Inspect or reinstall (see chapter 16).
Inspect (see chapter 16).
Inspect and replace (see chapter 2).
Replace it with the correct plug (see chapter 2).
Inspect (see chapter 3).
Supply fuel (see Owner’s Manual).
Clean element or inspect sealing (see chapter 2).
Reinstall (see chapter 3).
Reinstall (see chapter 3).
Replace (see chapter 3).
Replace (see chapter 3).

FUEL SYSTEM (DFI) 3-35
DFI System Troubleshooting Guide
Symptoms or Possible Causes
Fuel filter or pump screen clogged
Fuel pressure regulator trouble
Fuel line clogged
Intake air pressure sensor #1 or #2 trouble
Water temperature sensor trouble
Intake air temperature sensor trouble
Accelerator position sensor trouble
Throttle position sensor trouble
ETV actuator trouble
Unstable (rough) idling:
Fuel pressure too low or too high
Fuel injector trouble
Accelerator position sensor trouble
Throttle position sensor trouble
ETV actuator trouble
Intake air pressure sensor #1 or #2 trouble
Water temperature sensor trouble
Intake air temperature sensor trouble
Engine stalls easily:
Spark plug dirty, broken or gap maladjusted
Stick coil trouble
Accelerator position sensor trouble
Throttle position sensor trouble
ETV actuator trouble
Intake air pressure sensor #1 or #2 trouble
Water temperature sensor trouble
Intake air temperature sensor trouble
Fuel pump trouble
Fuel injector trouble
Fuel pressure too low or too high
Fuel pressure regulator trouble
Fuel line clogged
Poor acceleration:
Fuel pressure too low
Water or foreign matter in fuel
Fuel filter or pump screen clogged
Fuel pump trouble
Fuel injector trouble
Accelerator position sensor trouble
Throttle position sensor trouble

Actions (chapter)
Inspect and replace fuel filter or fuel pump (see
chapter 3).
Inspect fuel pressure and replace fuel pump (see
chapter 3).
Inspect and repair (see chapter 3).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect
Inspect
Inspect
Inspect
Inspect
Inspect
Inspect
Inspect

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chapter
chapter
chapter
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chapter
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3).
17).
17).
17).
17).
17).
17).
17).

Inspect and replace (see chapter 2).
Inspect (see chapter 16).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 3).
Inspect (see chapter 17).
Inspect (see chapter 3).
Inspect fuel pressure and replace fuel pump (see
chapter 3).
Inspect and repair (see chapter 3).
Inspect (see chapter 3).
Change fuel. Inspect and clean fuel system (see
chapter 3).
Inspect and replace fuel filter or fuel pump (see
chapter 3).
Inspect (see chapter 3).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).

3-36 FUEL SYSTEM (DFI)
DFI System Troubleshooting Guide
Symptoms or Possible Causes
ETV actuator trouble
Intake air pressure sensor #1 or #2 trouble
Water temperature sensor trouble
Intake air temperature sensor trouble
Spark plug dirty, broken or gap maladjusted
Stick coil trouble
Stumble:
Fuel pressure too low
Fuel injector trouble
Accelerator position sensor trouble
Throttle position sensor trouble
ETV actuator trouble
Intake air pressure sensor #1 or #2 trouble
Water temperature sensor trouble
Intake air temperature sensor trouble
Surge:
Unstable fuel pressure
–Fuel pressure regulator trouble
–Kinked fuel line
Fuel injector trouble
Water temperature sensor trouble
Backfiring when deceleration:
Spark plug dirty, broken or gap maladjusted
Fuel pressure too low
Fuel pump trouble
Accelerator position sensor trouble
Throttle position sensor trouble
ETV actuator trouble
Intake air pressure sensor #1 or #2 trouble
Water temperature sensor trouble
Intake air temperature sensor trouble
Air switching valve trouble
Air suction valve trouble
After fire:
Spark plug burned or gap maladjusted
Fuel injector trouble
Intake air pressure sensor #1 or #2 trouble
Water temperature sensor trouble
Intake air temperature sensor trouble
Other:
Intermittent any DFI fault and its recovery

Actions (chapter)
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect and replace (see chapter 2).
Inspect (see chapter 16).
Inspect
Inspect
Inspect
Inspect
Inspect
Inspect
Inspect
Inspect

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chapter
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17).
17).
17).
17).
17).
17).
17).

Inspect and replace fuel pump (see chapter 3).

Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect and replace (see chapter 2).
Inspect (see chapter 3).
Inspect (see chapter 3).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect and replace (see chapter 16).
Inspect and replace (see chapter 5).
Replace (see chapter 2).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Inspect (see chapter 17).
Check that DFI connectors are clean and tight,
and examine leads for signs of burning or fraying
(see chapter 17).

FUEL SYSTEM (DFI) 3-37
DFI System Troubleshooting Guide
Poor Running or No Power at High Speed
Symptoms or Possible Causes
Firing incorrect:
Stick coil shorted or not in good contact
Stick coil trouble
Spark plug dirty, broken or gap maladjusted
Spark plug incorrect
ECU trouble
Fuel/air mixture incorrect:
Air cleaner clogged, poorly sealed, or missing
Air intake duct loose
Throttle body assy holder loose
Throttle body assy O-ring damage
Water or foreign matter in fuel

Actions (chapter)
Inspect or Reinstall (see chapter 16).
Inspect (see chapter 16).
Inspect and replace (see chapter 2).
Replace it with the correct plug (see chapter 2).
Inspect (see chapter 3).

Clean element or inspect sealing (see chapter 2).
Reinstall (see chapter 3).
Reinstall (see chapter 3).
Replace (see chapter 3).
Change fuel. Inspect and clean fuel system (see
chapter 3).
Fuel injector O-ring damage
Replace (see chapter 3).
Fuel injector clogged
Inspect and repair (see chapter 3).
Fuel line clogged
Inspect and repair (see chapter 3).
Fuel pump operates intermittently and often DFI Fuel pump bearings may wear. Replace the fuel
fuse blows.
pump (see chapter 3).
Fuel pump trouble
Inspect (see chapter 3).
Intake air pressure sensor #1 or #2 trouble
Inspect (see chapter 17).
Cracked or obstructed intake air pressure sensor Inspect and repair or replace (see chapter 17).
#1 or #2 vacuum hose
Water temperature sensor trouble
Inspect (see chapter 17).
Intake air temperature sensor trouble
Inspect (see chapter 17).
Accelerator position sensor trouble
Inspect (see chapter 17).
Throttle position sensor trouble
Inspect (see chapter 17).
ETV actuator trouble
Inspect (see chapter 17).
Knocking:
Fuel poor quality or incorrect
Fuel change (Use gasoline recommended in
chapter 1 General Specifications).
Spark plug incorrect
Replace it with the correct plug (see chapter 2).