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Circuit/System Testing

    NOTE:

    Use the schematic to identify the following:

    • The device location on the high speed GMLAN serial data circuits
    • The device B+, ignition, ground, accessory wake up serial data 2 and serial data circuit terminals
  1. Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters (9.8 feet) away from vehicle. Disconnect the harness connector at the K20 engine control module. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between each ground circuit terminal and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 10 Ω 
  3. Ignition ON.
  4. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K20 engine control module.
    • If the test lamp illuminates 
  5. Ignition ON.
  6. If equipped, verify that a test lamp illuminates between each ignition circuit terminal and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is OK and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K20 engine control module.
    • If the test lamp illuminates 
  7. Ignition ON.
  8. If equipped, verify that a test lamp illuminates between the ignition circuit terminal, which is controlled by a control module, and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the harness connectors at the control module that controls the ignition circuit.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the control module that controls the ignition circuit.
    • If the test lamp illuminates 
  9. Ignition OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. Disconnect the low voltage harness connector at the K59 starter/generator control module. It may take up to 2 minutes for all vehicle systems to power down.
  10. Test for less than 2 Ω in each serial data circuit between the K20 engine control module and the K59 starter/generator control module.
    • If 2 Ω or greater 

      Repair the open/high resistance in the serial data circuit between the K20 engine control module and the K59 starter/generator control module.

    • If less than 2 Ω 
  11. Replace the K20 engine control module.
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