1. Turn the engine OFF.
2. Ensure that the engine temperature is cool.
3. Check the coolant level in the radiator and the reservoir.

Is the coolant level low?

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Go to Step 5

Go to Step 2

1. Connect the Scan Tool .
2. Start the engine.
3. Monitor the engine coolant temperature.

Does the coolant temperature increase steadily to the normal operating temperature?

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Go to Step 3

Go to Step 6

Feel the inlet and the outlet hoses of the heater core.

Do the inlet and the outlet hoses feel hot?

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Go to Step 4

Go to Step 7

Inspect the heater core for bent fins or other obstructions.

Did you locate and repair an obstruction?

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System OK

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1. Inspect the cooling system for signs of leakage. Refer to System Performance Test .
2. Fill the coolant system.
3. Bleed the air from the coolant system. Refer to Cooling System Draining and Filling .

Did you add coolant to the system?

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System OK

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Replace the faulty thermostat. Refer to Engine Coolant Thermostat Replacement in Engine Cooling.

Is the repair complete?

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System OK

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1. Inspect the hoses for kinks or other obstructions.
2. Flush or replace the obstructed heater core. Refer to Heater Core Replacement .

Is the repair complete?

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System OK

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