Alternate Instructions Operation Control (Fail-Safe Action); Fail-Safe Actions Table - Yamaha YP400T, YP400V, YP400W Service Manual

EAS00901
Checking for a defective engine trouble warning light bulb
The engine trouble warning light comes on for 1.4 seconds after the main switch has been turned
"ON" and when the start switch is being pushed. If the warning light does not come on under these
conditions, the warning light bulb may be defective.
Main switch
OFF
Engine trouble Light
warning light OFF
EAS00902

ALTERNATE INSTRUCTIONS OPERATION CONTROL (FAIL-SAFE ACTION)

If the ECU detects an abnormal signal from a sensor while the vehicle is being driven, the ECU illu-
minates the engine trouble warning light and provides the engine with alternate operating instruc-
tions that are appropriate for the type of malfunction.
When an abnormal signal is received from a sensor, the ECU processes the specified values that
are programmed for each sensor in order to provide the engine with alternate operating instructions
that enable the engine to continue to operate or stop operating, depending on the conditions.
The ECU takes fail-safe actions in two ways: one in which the sensor output is set to a prescribed
value, and the other in which the ECU directly operates an actuator. Details on the fail-safe actions
are given in the table below.

FAIL-SAFE ACTIONS TABLE

Fault
Item
code No.
Crankshaft position
12 sensor
Intake air pressure
13 sensor (open or short
14 circuit) (pipe system)
Throttle position sensor
15 (open or short circuit)
16 (stuck)
Broken or discon-
19 nected blue/yellow lead
of the ECU
Coolant temperature
21 sensor
Intake temperature
22 sensor
Faulty ignition
33
FUEL INJECTION SYSTEM
Main switch
ON
Light ON for Light
1.4 seconds OFF
Initialize
Symptom
No normal signals are
received from the crankshaft
position sensor.
Intake air pressure sensor-
open or short circuit detected.
Faulty intake air pressure sen-
sor pipe system.
Throttle position sensor-open
or short circuit detected.
A stuck throttle position sensor
is detected.
Open circuit in the input line
(blue/yellow lead) of the ECU
is detected.
Coolant temperature sensor-
open or short circuit is
detected.
Intake temperature sensor-
open or short circuit is
detected.
Open circuit detected in the
primary lead of the ignition
coil.
Fail-safe action
• Stops the engine (by stop-
ping the injection and igni-
tion).
• Fixes the intake air pres-
sure to 101.3 kPa
2
(1.01 kgf/cm , 14.4 psi).
• Fixes the throttle position
sensor to middle open.
-- (No start)
• Fixes the coolant tempera-
ture to 80 °C.
• Fixes the intake tempera-
ture to 20 °C.
--
7 - 4
FI
Engine start- Vehicle drive-
ability ability
Unable Unable
Able Able
Able Able
Unable Unable
Able Able
Able Able
Unable Unable