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Circuit/System Testing

    NOTE:

    Use the schematic to identify the following:

    • The control module location on the powertrain high speed GMLAN serial data circuits
    • The control module B+, ignition, ground, accessory wake up serial data 2 and serial data circuit terminals
  1. Ignition OFF, disconnect harness connector at the K20 engine control module (ECM).
  2. Test for less than 10 Ω between each ground circuit terminal and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal 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 fuse is open, test the control circuits of the K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal 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 fuse is open, test the control circuits of the K20 ECM for a short to ground. If the circuits test normal, replace the K20 ECM.
  5. If equipped, ignition ON, verify that a test lamp illuminates between the accessory wake up serial data circuit terminal and ground.
    • If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  6. Ignition OFF, disconnect the low voltage harness connector at the control module setting the DTC.
  7. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 Ω in each serial data circuit between the K20 ECM and the control module setting the DTC.
    • If greater than the specified range, test the serial data circuit for an open/high resistance between the K20 ECM and the control module setting the DTC.
  8. If the circuits test normal, replace the K20 ECM.
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