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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 2002 (Hybrid Cooling System - 3.6L (Hp5)) >> Diagnostic Information and Procedures >> Hybrid Cooling System Overheating >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Disconnect the coolant pump relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the relay controlled output circuit terminal 87 and ground.
    • If the test lamp illuminates, test the relay controlled output circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the relay coil B+ circuit terminal 85 and ground.
    • If the test lamp does not illuminate, test the relay coil B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay coil B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the coolant pump relay.
  4. Verify that a test lamp illuminates between the relay switch B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate, test the relay switch B+ circuit for an open/high resistance.
  5. Disconnect the harness connector at the appropriate DMCM coolant pump.
  6. Test for less than 5.0 ohms between the coolant pump ground circuit terminal 1 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the coolant pump.
  8. Connect a 15 A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay controlled output circuit terminal 87. Verify the coolant pump is activated.
    • If the coolant pump does not activate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal, test or replace the coolant pump.
  9. Connect a test lamp between the relay coil B+ circuit terminal 85 and the relay coil control circuit terminal 86.
  10. Command the DMCM coolant pump ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the ECM.
    • If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  11. If all circuits test normal, test or replace the relay.
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