Komatsu PC200-8M0, Shop Manual

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301 Troubleshooting by failure code, Part 1
Failure code [CA123] Chg Air Press Sensor Low Error
40-301
22
PC200, 200LC, 220, 220LC-8M0
SEN06133-00
Failure code [CA123] Chg Air Press Sensor Low Error
*: See "Troubleshooting method for open circuit in wiring harness of pressure sensor system" of "General in-
formation on troubleshooting".
Action
level
Failure code
Failure
Charge Air Pressure Sensor Low Error
(Engine controller system)
L03 CA123
Detail of failure q Low voltage appears in pressure signal circuit of charge (boost) pressure & temperature sensor.
Action of con-
troller
q
Takes boost pressure to be at fixed value and allows engine to run.
Problem on
machine
q Engine output lowers.
Related infor-
mation
q
Input voltage from boost pressure sensor can be checked with monitoring function.
(Code:
36501 (V) )
q
Boost pressure sensed by boost pressure sensor can be checked with function.
(Code:
36500 (kPa) )
q
Method of reproducing failure code: Turn starting switch to ON position.
q
Since troubleshooting "socket" for this sensor features female connector alone, it is not usable for
checking open circuit in wiring harness and voltage at sensor connector (not designed as a
T-adapter).
q
If sensor connector is disconnected, this failure code is displayed.
Cause Procedure, measuring location, criteria and remarks
1
Defective wiring harness connec-
tor
See descriptions of wiring harness and connectors in "c: Electrical equipment"
in "Checks before troubleshooting" of "General information on troubleshoot-
ing", and check them.
2
Defective power supply system of
charge pressure sensor (boost
pressure sensor)
If failure code [ CA187 ] or [ CA227 ] is displayed, perform troubleshooting for it
first.
3 Short circuit in wiring harness
1. Turn starting switch to OFF position.
2. Disconnect connectors CAM SENSOR, FUEL RAIL PRESS, BOOST
PRESS & IMT and ECM.
3. Connect T-adapters to female side of ECM.
Between ECM (female) (37) and (47) Resistance Min. 100 k
z
Between ECM (female) (44) and (47) Resistance Min. 100 k
z
4
Ground fault in wiring harness
(contact with ground circuit)
1. Turn starting switch to OFF position.
2. Disconnect connectors ECM and BOOST PRESS & IMT, and connect
T-adapter to female side of ECM.
Between ECM (female) (44) and ground Resistance Min. 100 k
z
5 Open circuit in wiring harness
If no failure is found by above checks, there may be open circuit in wiring har-
ness. (*)
6
Defective boost pressure & tem-
perature sensor
(improper input voltage to engine
controller)
a
If no failure is found by checks on causes 1 to 5 and check result on cause
6 is abnormal, sensor is defective.
1. Turn starting switch to OFF position.
2. Insert T-adapters to connector ECM.
3. Turn starting switch to ON position.
Between ECM (44) and (47)
Sensor out-
put
Voltage 0.3 to 4.7 V
7 Defective engine controller
If no failure is found by above checks, engine controller is defective. (Since
this is an internal defect, troubleshooting cannot be performed.)