Code [778/Ca778] Eng. Bkup Speed Sensor Error - Komatsu 114E-3 Series Shop Manual

SEN00460-01
E-47 Code [778/CA778] Eng. Bkup Speed Sensor Error
Error code Failure code
778
Contents of
• Abnormality is detected in signals of engine Bkup speed sensor.
trouble
Action of con-
• Controls with signals of Ne speed sensor.
troller
Problem that
• Starting performance is poor
appears on
• Output drops.
machine
Related infor-
• Method of reproducing failure code: Start engine.
mation
Defective sensor power sup-
1
ply 2 system
Defective engine Bkup speed
2
sensor
Broken engine Bkup speed
3
sensor or defective clearance
4 Broken rotation sensing ring Inspect it for breakage directly.
Disconnection in wiring har-
ness (Disconnection in wiring
5
or defective contact in con-
nector)
Possible causes
and standard Ground fault in wiring har-
value in normal
6 ness (Short circuit with GND
state
circuit)
Hot short (Short circuit with
7 5V, 24V circuit) in wiring har-
ness
Short circuit in wiring harness
8
(With another wiring harness)
Defective wiring harness
9
connector
38
Trouble Abnormality in engine Bkup speed sensor
CA778
Causes Standard value in normal state/Remarks on troubleshooting
If failure code [CA187] is indicated simultaneously, carry out trouble-
shooting for it first.
a Prepare with starting switch OFF, then turn starting switch ON and
carry out troubleshooting.
CAM SENSOR
Between (1) – (2)
Voltage is measured with wiring harness connected. Accordingly, if
voltage is abnormal, check wiring harness and controller, too, for
another cause of trouble, and then judge.
Inspect engine Bkup speed sensor directly for breakage or clear-
ance.
a Prepare with starting switch OFF, then carry out troubleshooting
without turning starting switch ON.
Wiring harness between J1 (female) (26) –
CAM SENSOR (female) (3)
a Prepare with starting switch OFF, then carry out troubleshooting
without turning starting switch ON.
Wiring harness between J1 (female) (26) –
CAM SENSOR (female) (3)
a Prepare with starting switch OFF, then turn starting switch ON and
carry out troubleshooting.
Wiring harness between J1 (female) (26) –
CAM SENSOR (female) (3)
a Prepare with starting switch OFF, then carry out troubleshooting
without turning starting switch ON.
Wiring harness between J1 (female) (26) –
CAM SENSOR (female) (3) and J1 (female)
(37) – CAM SENSOR (female) (1)
Wiring harness between J1 (female) (26) –
CAM SENSOR (female) (3) and J1 (female)
(47) – CAM SENSOR (female) (2)
Connecting parts among engine Bkup speed sensor, engine wiring
harness, and engine controller are suspected. Inspect them directly.
• Loose connector, broken lock, broken seal
• Corrosive, bent, broken, forced-in, or extended pin
• Humidity in connector, entry of dirt or dust, poor insulation
40 Troubleshooting
Power supply 4.75 – 5.25 V
Resis-
tance
Resis-
tance
Voltage
Resis-
tance
Resis-
tance
114E-3 Series
1
Voltage
Max. 10 z
Min.
100 kz
Max. 1 V
Min.
100 kz
Min.
100 kz