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Circuit/System Testing

    NOTE:

    Use the schematic to identify the following:

    • The control module location on the 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 harness connector at the K59 starter/generator control module.
  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 K59 starter/generator control module.
    • If greater than the specified range, test the serial data circuit for an open/high resistance between the K20 ECM and the K59 starter/generator control module.
  8. If the circuits test normal, replace the K20 ECM.
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