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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1655 (Engine Control System & Fuel System - Hybrid (Hp2) 6.0L (LZ1) - DTC P1380 To DTC P3449) >> DTC P1682 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
    NOTE:
    • The ignition 1 signal is supplied by the Run/Crank relay. The EC ignition relay feedback signal is supplied by the powertrain relay.
    • High resistance in the ignition 1 signal or EC ignition relay feedback circuit/underhood fuse block will cause the DTC to set.
  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. 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 B+.
    • If not the specified value, or the ECM does not communicate, test the ignition voltage circuit between the powertrain relay and the ECM for a short to ground or 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 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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