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Home >> Hummer >> 2010 >> H3 Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 3.7L - DTC P0335 To DTC P1381 >> DTC P0412 or P0418 >> Circuit/System Testing
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Circuit/System Testing

  1. Ignition OFF, remove the appropriate relay.
  2. Ignition ON, verify that a test lamp illuminates between the relay coil B+ circuit terminal 86 and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
  3. Verify a test lamp does not illuminate between the relay control circuit terminal 85 and B+.
    • If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  4. Test for less than 1 V between the relay coil control circuit terminal 85 and ground.
    • If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Connect a DMM set to the diode setting between the control circuit terminal 85 and ground.
  6. Command the appropriate relay ON and OFF with a scan tool. The DMM should transition from 2.5-3.5 V when commanded OFF to less than 1 V when commanded ON.
    • If the circuit voltage does not correspond to the specified values, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  7. If all circuits test normal, test or replace the appropriate relay.
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