Table 11
Troubleshooting Test Steps Values Results
1. Diagnostic Codes
A. Use the electronic service tool to check for diagnostic codes that
relate to the temperature in the cooling system.
Diagnostic
Codes
Result: Diagnostic codes are not present.
Return the unit to service.
Result: Diagnostic codes are present.
Proceed to Test Step 2.
2. Coolant Level
A. Check the coolant level.
Engine coolant
level Result: The engine coolant level is low.
Check the cooling system for leaks. Refer to Systems Op-
eration, Testing and Adjusting, “Cooling System - Test” for
additional information. Repair any leaks immediately.
Result: The engine coolant level is OK.
Proceed to Test Step 3.
3. Coolant Temperature Sensor
A. Compare the reading for the coolant temperature on the elec-
tronic service tool to the reading for the coolant temperature on a
calibrated test gauge.
Coolant tem-
perature sensor
Result: The temperature sensor is not accurate.
Troubleshoot the circuit and the coolant temperature sen-
sor. Refer to Troubleshooting, “Sensor Signal (Analog,
Passive) - Test”.
Result: The temperature sensor is reading accurately.
Proceed to Test Step 4.
4. Radiator and Hoses
A. Check the radiator fins for dirt, debris, and/or damage.
B. Check for collapsed hoses and/or other restrictions.
C. Check the radiator for internal blockage.
D. Ensure that the radiator size is sufficient. An undersized radiator
does not have enough area for the effective release of heat. An un-
dersized radiator may cause the engine to run at a temperature that
is higher than normal. The normal temperature is dependent on the
ambient temperature.
Radiator and
hoses
Result: The radiator fins are blocked or damaged.
Remove any dirt and/or debris and straighten any bent
fins.
Result: The radiator has internal blockage.
Remove the blockage.
Result: The radiator fins are not damaged and the radiator
does not have an internal blockage.
Proceed to Test Step 5.
5. Radiator Cap and Pressure Relief Valve
A. Pressure-test the cooling system. Refer to Systems Operation,
Testing, and Adjusting, “Cooling System” for the correct procedure.
B. Check that the seating surfaces of the pressure relief valve and
the radiator cap are clean and undamaged.
C. Check operation of the pressure relief valve and/or the water
temperature regulator.
Radiator cap Result: The pressure relief valve and/or the water temper-
ature regulator are not operating properly.
Clean the components or replace the components.
Result: The pressure relief valve and/or the water temper-
ature regulator are operating properly.
Proceed to Test Step 6.
(continued)
40 UENR0612
Symptom Troubleshooting
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