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Circuit/System Testing

WARNING: This page is about a different car, the 2009 Chevrolet HHR. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the cooling fan relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the relay.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  5. Disconnect the harness connector at the cooling fan.
  6. Test for less than 1.0 ohm between the cooling fan ground circuit terminal A and ground
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the cooling fan.
  8. Connect a 30A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the cooling fan is activated.
    • If the cooling fan does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the cooling fan.
  9. Verify that a test lamp does not illuminate between the B+ circuit terminal 85 and the control circuit terminal 86.
    • If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  10. Ignition OFF, allow the ECM to completely power down.
  11. Test for 70-110 ohms between terminals 85 and 86 of the cooling fan relay.
    • If the resistance is not within the specified range, replace the relay.
  12. Measure amperage with a DMM connected in series with the relay coil and a 3A fused jumper wire between the B+ circuit terminal 85 and the control circuit terminal 86.
  13. Ignition ON, command the relay ON and OFF with a scan tool. The DMM should indicate less than 1 mA with the relay commanded OFF and approximately 170 mA with the relay commanded ON.
    • If the DMM does not indicate the specified values, test the control circuit for an open or a short to voltage. If the circuit tests normal, replace the ECM.
  14. If all circuits test normal, test or replace the cooling fan relay.
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