GM Service Manual Online
For 1990-2009 cars only

The optional engine coolant heater (RPO KO5) is designed to warm the coolant in the engine block area for improved starting in very cold weather (-29°C/-20°F). The use of a coolant heater helps reduce fuel consumption when a cold engine is warming up. The engine coolant heater coil is rated at 600 watts. The engine coolant heater coil operates from 110 volt AC external power supply.

The coolant heater consists of one electrical heating element inserted in the left side of the engine block. The heating elements are precisely machined. A weather shield on the cord is provided to protect the plug when not in use.

Check the following if the coolant heater fails to heat the coolant:

  1. Check for 110 volt AC external power source.
  2. Check for continuity to ground of heater cord.
  3. Check for shorts to ground of heater cord.
  4. Replace cord as required.
  5. Check the heating element if the external power source and the cord are OK.
  6. The heating element should show continuity.
  7. Replace as required.