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Circuit/System Testing

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  1. Test the thermostat for correct operation. Refer to Thermostat Diagnosis .
  2. Test the engine cooling system for overheating. Refer to Engine Overheating .
  3. Inspect the water pump and coolant flow for correct operation. Refer to Water Pump Replacement (RPOs LY2/LC9/LY5/LMG/LFA)  or Water Pump Replacement (RPOs LY6/L76/L92) .
  4. Inspect the engine for worn/leaking/cracked cylinder heads and engine block. Refer to Coolant in Combustion Chamber and Coolant in Engine Oil .
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