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Home >> Cadillac >> 2021 >> XT5 Sport >> Repair and Diagnosis >> External Pages >> Different car >> Section 19 (Cellular, Entertainment, And Navigation System) >> Diagnostic Information and Procedures >> DTC B123A-B123C >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2020 Cadillac XT5. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, radio OFF.
  2. Disconnect the X1 harness connector at the T3LF Audio Amplifier - Left Front.
  3. Test for less than 10 Ω between the ground circuit terminal 16 and ground.
    • If 10 Ω or greater 
    1. Disconnect the ground connection at G206
    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 
  4. Verify a test lamp illuminates between the B+ circuit terminal 8 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition 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 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.
    • Go to next step: If the test lamp illuminates 
  5. Ignition ON/Vehicle in Service Mode. Radio ON.
  6. Test for 2.5 - 3.5 V between the control circuit terminal 4 and ground:
    • If less than 2.5 V 
    1. Ignition OFF, disconnect the appropriate harness connector at the T3 Audio Amplifier.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the T3 Audio Amplifier.
    • If greater than 3.5 V 
    1. Ignition OFF, disconnect the appropriate harness connector at the T3 Audio Amplifier.
    2. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the T3 Audio Amplifier.
    • Go to next step: If between 2.5 - 3.5 V. 
  7. Test or replace the T3LF Audio Amplifier - Left Front.
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