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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 P0685 or P0690 >> Circuit/System Testing
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Circuit/System Testing

NOTE: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
  1. Ignition OFF, disconnect the KR75 powertrain relay.
  2. Verify a test lamp illuminates between both of the following relay battery voltage circuit terminals and ground:
    • Terminal 85
    • Terminal 30
    • If the test lamp does not illuminate, test the relay battery voltage circuit for an open/high resistance or a short to ground.
    3. NOTE: The ignition voltage circuit is between the powertrain relay and the ECM. The ignition voltage is a feedback circuit.
  3. Ignition OFF, verify that a test lamp does not illuminate between the ignition voltage circuit terminal 87 and ground.
    • If the test lamp illuminates, test the ignition voltage circuit for a short to voltage.
  4. Connect a 20 A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay switch ignition voltage circuit terminal 87.
  5. Ignition ON, observe the scan tool EC Ignition Relay Feedback Signal parameter. The ECM should communicate, and the parameter should display 9-14 V.
    • If not the specified range, or the ECM does not communicate, test the ignition voltage circuit between the powertrain relay and the ECM for a short to ground or for an open/high resistance. If the circuit/connections test normal, replace the K20 ECM.
  6. Ignition OFF, verify that a test lamp does not illuminate between the control circuit terminal 86 and B+.
    • If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.
  7. Connect a DMM set to the diode setting between the control circuit terminal 86 and ground.
  8. Ignition ON, verify the DMM does not display OL.
    • If the DMM displays OL, test the control circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
  9. If all circuits test normal, replace the KR75 powertrain relay.
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