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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1284 (Engine Cooling System) >> Diagnostic Information and Procedures >> Coolant Heater Inoperative (Gasoline) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT: The power supply cord will read open due to an internal thermal switch if the ambient temperature is above -18°C (0°F).
  1. Test the engine coolant heater for an open or short to ground.
    • If open or shorted, replace the heater.
  2. If the heater tests normal, replace the coolant heater power cord.
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