Troubleshooting

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.
Repair: Check the cooling system for leaks. Refer to Sys-
tems Operation, 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.
Repair: Troubleshoot the circuit and the coolant tempera-
ture sensor. 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.
Repair: Remove any dirt and/or debris and straighten any
bent fins.
Result: The radiator has internal blockage.
Repair: Remove the blockage.
Result: The radiator fins are not damaged and the radia-
tor 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 tem-
perature regulator are not operating properly.
Repair: Clean the components or replace the
components.
Result: The pressure relief valve and/or the water tem-
perature regulator are operating properly.
Proceed to Test Step 6.
(continued)
40 UENR0612-07
Symptom Troubleshooting
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