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Circuit/System Testing

NOTE:

Use the schematics and connector end views to identify the device's ground, B+, ignition, serial data communication enable, and serial data circuit terminals.

  1. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. Disconnect the harness connectors at the K56 Serial Data Gateway Module. It may take up to 10 min 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/Vehicle 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.
    • Go to next step: If less than 10 Ω 
  3. If equipped, verify 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/Vehicle OFF, remove the test lamp.
    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/Vehicle OFF, remove the test lamp.
    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 K56 Serial Data Gateway Module.
    • Go to next step: If the test lamp illuminates 
  4. Ignition ON/Vehicle In Service Mode.
  5. If equipped, verify a test lamp illuminates between each ignition circuit terminal, which has a fuse in the circuit, and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition/Vehicle OFF, remove the test lamp.
    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/Vehicle OFF, remove the test lamp.
    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 K56 Serial Data Gateway Module.
    • Go to next step: If the test lamp illuminates 
  6. Verify a test lamp illuminates between the serial data communication enable circuit terminal and ground.
    • If the test lamp does not illuminate 
    1. Ignition/Vehicle OFF, remove the test lamp, disconnect the harness connectors at the K9 Body Control Module.
    2. Test for less than 2 Ω in the serial data communication enable circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • Go to next step: If the test lamp illuminates 
  7. Test for less than 4.5 V between each GMLAN serial data circuit terminal listed below and ground:
    • Terminal 13 X1
    • Terminal 14 X1
    • Terminal 15 X1
    • Terminal 16 X1
    • Terminal 17 X1
    • Terminal 18 X1
    • Terminal 26 X1
    • If 4.5 V or greater 

      Repair the short to voltage in the serial data circuit.

    • Go to next step: If less than 4.5 V 
  8. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 10 min for all vehicle systems to power down.
  9. Test for infinite resistance between each GMLAN serial data circuit terminal listed below and ground:
    • Terminal 13 X1
    • Terminal 14 X1
    • Terminal 15 X1
    • Terminal 16 X1
    • Terminal 17 X1
    • Terminal 18 X1
    • Terminal 26 X1
    • If less than infinite resistance 

      Repair the short to ground in the serial data circuit.

    • Go to next step: If infinite resistance 
  10. Test for infinite resistance between each pair of the GMLAN serial data circuit terminals listed below and ground:
    • Terminals 13 X1 and 14 X1
    • Terminals 15 X1 and 16 X1
    • Terminals 17 X1 and 18 X1
    • If less than infinite resistance 

      Repair the short together in the serial data circuits.

    • Go to next step: If infinite resistance 
  11. Test for less than 2 Ω in each GMLAN serial data circuit end to end between the K56 Serial Data Gateway Module and the X84 Data Link Connector.
    • If 2 Ω or greater 

      Repair the open/high resistance in the serial data circuit.

    • Go to next step: If less than 2 Ω 
  12. Replace the K56 Serial Data Gateway Module.
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