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Home >> Cadillac >> 2017 >> CT6 Plug-In >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Infotainment >> Cellular System, Entertainment System And Navigation System - Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> DTC B123A-B123C: Audio Amplifier Control Circuit >> Circuit/System Testing

Circuit/System Testing

B123A or B123B 

  1. Ignition OFF, radio OFF.
  2. Disconnect the X1 harness connector at the appropriate Secondary Audio Amplifier.
  3. Test for less than 10 Ω between the test points: Ground circuit terminal 6 & Ground
    • If 10 Ω or greater 
    1. Disconnect the ground connection: G305
    2. Test for less than 2 Ω between the test points: Ground circuit terminal 6 & Ground
      • 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 
  4. Verify a test lamp turns On between the test points: B+ circuit terminal 8 & 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.
    • 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 2 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.
      • 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.
    • If between 2.5-3.5 V. 
  7. Test or replace the Secondary Amplifier/Subwoofer Enclosure

B123C 

  1. Ignition OFF, radio OFF.
  2. Disconnect the X1 harness connector at the appropriate Secondary Audio Amplifier.
  3. Test for less than 10 Ω between the test points: Ground circuit terminal 14 & Ground
    • If 10 Ω or greater 
    1. Disconnect the ground connection: G305
    2. Test for less than 2 Ω between the test points: Ground circuit terminal 14 & Ground
      • 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 
  4. Verify a test lamp turns On between the test points: B+ circuit terminal 7 & 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.
    • 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 5 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.
      • 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.
    • If between 2.5-3.5 V. 
  7. Ignition OFF, Reconnect harness connector at the appropriate Secondary Audio Amplifier. Disconnect the harness connector at the P19AC Speaker, Ignition ON/ Vehicle in Service Mode. Infotainment system ON, mute OFF.
  8. Test for 3-8 V between the appropriate signal circuit terminals listed below and ground.
    • Rear Subwoofer (-) circuit terminal A
    • Rear Subwoofer (+) circuit terminal B
    • If less than 3 V 
    1. Ignition OFF, disconnect the appropriate harness connector at the Secondary Audio Amplifier.
    2. Test for infinite resistance between the signal 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 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 Secondary Audio Amplifier.
    • If greater than 8 V 
    1. Ignition OFF, disconnect the appropriate harness connector at the Secondary Audio Amplifier.
    2. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the Secondary Audio Amplifier.
    • If between 3-8 V 
  9. Test or replace the P19AC Speaker
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