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Circuit/System Testing

NOTE: Use the schematic to identify the following:
  • Control modules the vehicle is equipped with
  • Control module locations on the mid speed GMLAN serial data circuit
  • The control modules B+, ignition, ground, communication enable and serial data circuit terminals
  1. Ignition OFF, disconnect the harness connector of the radio.
  2. Test for less than 5 Ω between each ground circuit terminal and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. 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 for a short to ground. If the circuits test normal, replace the radio.
  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 for a short to ground. If the circuits test normal, replace the radio.
  5. Ignition OFF for 60 seconds, test for less than 5 Ω between the radio connector terminals and DLC terminals listed below:
    • Radio connector terminal 9 and DLC terminal 3
    • Radio connector terminal 10 and DLC terminal 11
    • If greater than the specified range, test the serial data circuit for an open/high resistance between the radio and a module setting the DTC.
  6. If all circuits test normal, replace the radio.
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