Failure Code [Ca778] Engine Backup Speed Sensor Error - Komatsu PC88MR-10 Shop Manual

Failure code [CA778] Engine Backup Speed Sensor Error

Action level Failure code
L01 CA778
Detail of
Engine Bkup speed (CAM) sensor signal is abnormal.
failure
Action of
Continues to control engine by using engine Ne speed sensor signal.
controller
Engine startability is poor
Problem on
Engine output loweres.
machine
Method of reproducing failure code: Start engine.
Since interior portion of speed sensor is configured with hall sensor and electronic circuit
rather than coil, measurements of speed sensor resistance by using mulitimeter cannot
be used to determine whether sensor is normal or not.
Related
Since speed sensor output is pulse voltage of 5 V in normal state, multimeter is not usable
information
for measurement.
This speed sensor detects groove in speed sensing ring, which is installed to camshaft, to
measure camshaft speed.
No. Cause
Defective wiring
1
harness connector
Defective sensor power
2
supply 2 circuit
Breakage or improper
installation (loosened)
3
of engine Bkup speed
(CAM) sensor
Improper power supply
input to engine Bkup
4
speed sensor
Open circuit in wiring
harness
5
(wire breakage or
defective contact of
connector)
Short circuit in wiring
6
harness
Ground fault in wiring
harness
7
(contact with ground
circuit)
PC88MR-10
Engine Backup Speed Sensor Error
Failure
(Engine controller system)
Procedure, measuring location, criteria and remarks
1. See descriptions of wiring harness and connectors in "c: Electrical
equipment" in "Checks before troubleshooting" of "Related information on
troubleshooting", and check it.
2. Turn starting switch to ON position.
If this failure code is not displayed, wiring harness connector is defective.
a If this failure code is displayed, perform following checks.
If failure code [CA187] or [CA227] is also displayed, perform troubleshooting
for it first.
Engine Bkup speed (CAM) sensor may be broken or installed improperly
(loosened). Check it.
1. Turn starting switch to OFF position.
2. Disconnect connector CAM, and connect T-adapter to female side.
3. Turn starting switch to ON position.
Power
Between CAM (female) (1) and (2)
supply
Voltage Between CAM (female) (1) and (2)
1. Turn starting switch to OFF position.
2. Disconnect connectors J1 and CAM, and connect T-adapters to each
female side.
Between J1 (female) (60) and CAM (female) (1)
Between J1 (female) (59) and CAM (female) (2)
Resistance
Between J1 (female) (9) and CAM (female) (3)
1. Turn starting switch to OFF position.
2. Disconnect connectors J1 and CAM, and connect T-adapter to either
female side.
Between J1 (female) (9) and (60), or between CAM
(female) (1) and (3)
Resistance
Between J1 (female) (9) and (59), or between CAM
(female) (2) and (3)
1. Turn starting switch to OFF position.
2. Disconnect connectors J1 and CAM, and connect T-adapter to either
female side.
Between ground and J1 (female) (9) or CAM
Resistance
(female) (3)
40 Troubleshooting
Troubleshooting by failure code (Display of code)
(PC88MR-CA778-400-A-Z0-A)
4.75 to 5.25
V
4.75 to 5.25
V
Max. 1 z
Max. 1 z
Max. 1 z
Min. 1 Mz
Min. 1 Mz
Min. 1 Mz
40-205