Komatsu PC200-8M0, Shop Manual

Page: 598 / 1254

301 Troubleshooting by failure code, Part 1
Failure code [CA144] Coolant Temp Sens High Error
40-301
28
PC200, 200LC, 220, 220LC-8M0
SEN06133-00
Failure code [CA144] Coolant Temp Sens High Error
Action
level
Failure code
Failure
Coolant Temperature Sensor High Error
(Engine controller system)
L01 CA144
Detail of failure q High voltage appears in signal circuit of coolant temperature sensor .
Action of con-
troller
q
Takes coolant temperature to be at fixed value and allows engine to run.
Problem on
machine
q
Engine does not start easily at low temperature.
q
Overheat prevention function does not work.
Related infor-
mation
q
Input voltage from engine coolant temperature sensor can be checked with monitoring function.
(Code:
04105 (V) )
q
Temperature sensed by engine coolant temperature sensor can be checked with monitoring func-
tion.
(Code:
04107 (°C ))
q
Method of reproducing failure code: Turn starting switch to ON position.
q
This failure code is displayed if temperature sensor connector is disconnected.
q
Because troubleshooting "socket" for this sensor features female connector alone, it is not connect-
able to female connector of sensor wiring harness, and thus not usable for checking open circuit
(not designed as a T-adapter).
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 coolant temperature
sensor
1. Turn starting switch to OFF position.
2. Disconnect connector COOLANT TEMP, and connect socket to male side.
a
If coolant temperature sensor has resistance of 700
z
- 37 k
z
with coolant
temperature above 0 °C, regard coolant temperature sensor as normal.
Between COOLANT
TEMP (male) (A) and (B)
a
Coolant temperature
-Resistaure charac-
teristics
0 °C Resistance 30 to 37 k
z
25 °C Resistance 9.3 to 10.7 k
z
50 °C Resistance 3.2 to 3.8 k
z
80 °C Resistance 1.0 to 1.3 k
z
95 °C Resistance 700 to 800
z
3
Open or short circuit in wiring har-
ness
1. Turn starting switch to OFF position.
2. Disconnect connector ECM and connect T-adapters to female side.
Between ECM (female) (15) and (38) (Coolant tem-
perature: Min. 0°C)
a
Use "Coolant temperature-Resistance charac-
teristics" table shown above as resistance crite-
ria.
Resis-
tance
700
z
to 37 k
z
4 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.)