Doosan D20S-7 - Page 99

Operation Section
-96-
Diagnosis Chart by Symptom (Cont'd)
Symptoms
Impossible
to start
Poor starting
Poor idle Poor driving control Engine stall Other
Check that symptoms are detected with self-diagnosis.
Check that symptoms are in fall-safe condition.
Sensor malfunction
⊕: Highly possible
◆: Possible
No initial combustion
Initial combustion
When en
g
ine is cold
When en
g
ine is warmin
g
up
Fast idle is not effective
High idle rpm
Low idle rpm
Inconsistent idle when engine is cold.
Inconsistent idle when warming up
Poor power output
Poor acceleration
Engine rpm does not increase smoothly.
During surge and acceleration
During surge and constant speed driving
Knocking
Backfire
After-burn
At Idle
Driving
During deceleration
During a heavy load
Engine over temperature (Overheat)
Poor fuel consumption efficiency
Description/notable
characteristics
of the symptom
Vehicle
speed
sensor
OPEN/
SHORT
◆ ◆◆ ◆
• Duration of fuel cut becomes
SHORT shorter or fuel may
not be cut.
Throttle
position
sensor
OPEN/
SHORT
◆ ◆◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆◆ ◆ ◆
• Idle will be base rpm. No
SHORT addition for
acceleration.
Output
Fluctuation
◆ ◆◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆
• Possible interruption by
fluctuation unnecessary fuel
injection. Poor ground or
control unit connection may
be the cause.
Poor
adjustme
nt
◆ ◆
• Idling is judged as OFF
during adjustment idle.
Turning ignition switch
repeatedly to ON and OFF
will sell the system to normal.
Accelerator
pedal
position
sensor
OPEN/
SHORT
◆ ◆◆ ◆ ◆ ◆ ◆◆
Output
Fluctuation
◆ ◆◆ ◆ ◆ ◆ ◆
Ignition
switch
IGN
OP
EN
⊕ ⊕ ⊕ ⊕ ⊕
• Impossible to start without
outputs for fuel and ignition
systems.
Neutral SW
OPEN ◆ ⊕ ◆ ⊕ ◆ ◆ ◆
• Neutral switch is judged as
OFF, and the target cold
engine speed in NIP position
is lowered.
SHORT
• Neutral switch is judged as
ON, and fast idle is effective
for cold engine in positions
other than N/ P position,
making the creep
larger.
Stop lamp
switch
OPEN/
SHORT
Headlamp
(electrical
load)
switch
OPEN/
SHORT
◆ ◆
Power
supply
for ECM
OPEN ⊕ ⊕ ⊕ ⊕ ⊕ ◆
• Impossible to start without
outputs for fuel and ignition
systems.