Coolant Temperature Sens, Short To High Source - New Holland CX720 Repair Manual

0399.3-COOLANT TEMPERATURE SENS, SHORT TO HIGH SOURCE

(SERVICE TOOL FAULT CODE 148) (B.50.A.95.90 - G.30.B.54)
CX860, CX880
0399.3 - COOLANT TEMPERATURE SENS, SHORT TO HIGH SOURCE (SERVICE TOOL FAULT CODE 148)
Context:
Engine enabled - no restriction on fuel or speed
Cause:
Signal range outside threshold limits
Signal not plausible or intermittent fault
Possible failure modes:
1. Faulty coolant sensor
2. Faulty connector or wiring
Solution:
1. Check the engine Coolant level
A. Ensure the coolant level is within the min/max indicators. Adjust as required. If the level was very low,
i.e., no fluid visible in the header tank, investigate the cause of the fluid loss and repair. Remove the fault
code from the ECU memory, using the electronic service tool and operate the engine, if the fault does not
reoccur continue with vehicle operation.
B. If the fault reoccurs continue with step 2
2. Check connector at sensor.
A. Ensure the connector is not damaged, the terminals are in the correct position in the housing, and that the
fit is tight on the sensor. Repair or replace damaged components as required.
B. If the connector is okay continue with step 3.
3. Check sensor.
A. Remove the connector and check the sensor using a suitable multi-meter. Measure the resistance across
the sensor terminals, the resistance should vary between 8 - 10 kΩ at -10 °C, 2.2 - 2.7 kΩ at 20 °C and
0.29 - 0.36 kΩ at 80 °C. Check for a short to ground between each sensor terminal and the engine block,
an open circuit should be recorded on each terminal. If any readings are incorrect replace the sensor.
B. If the sensor is okay continue with step 4.
4. Check wiring
A. Disconnect the sensor connector. With the key start switch ON, measure the voltage at pin 2 (blue wire),+5
V should be measured. If no voltage is measured check the wiring for continuity between Pin 2 of the
sensor connector, X214 and pin 5 of engine ECU connector X192. Repair wiring as required. Check for
voltage on Pin 1 ,0 V should be measured. If voltage is measured trace and repair short circuit in wiring
between Pin 1 of the sensor connector and Pin 22 of the engine ECU connector X192. With the key start
OFF, also check for continuity of the wire between Pin 1 of the sensor connector and Pin 22 of the engine
ECU connector X192, and for a short to ground. Trace fault and repair as required.
B. If the wiring is okay suspect a faulty engine ECU. Download engine software using the electronic service
tool and operate engine. If fault still occurs substitute engine ECU.
Series 1206 and above
Wiring harness - Electrical schematic frame 04 (A.30.A.88-C.20.E.04)
POWER PRODUCTION - ENGINE COOLANT SYSTEM
2 4/7/2006
B.50.A / 56