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Home >> Cadillac >> 2017 >> ATS Base, 4D Sedan, RWD, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 174 (Cellular System, Entertainment System, And Navigation System - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC B123A-B123C: Audio Amplifier Control >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2016 Cadillac CT6. However, it is still accessible from the selected car via links, so may be relevant.

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 ohm; between the test points:Ground circuit terminal 6 &Ground
    • If 10 ohm; or greater 
    1. Disconnect the ground connection:G305
    2. Test for less than 2 ohm; between the test points:Ground circuit terminal 6 @Component harness&Ground
      • If 2ohm; or greater » Repair the open/high resistance in the circuit.
      • If less than 2ohm; » Repair the open/high resistance in the ground connection.
    • If less than 10 ohm; 
  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 2 ohm; between the test points:Ground circuit terminal 14 & Ground
    • If 10 ohm; or greater 
    1. Disconnect the ground connection:G305
    2. Test for less than 2 ohm; between the test points:Ground circuit terminal 14 @Component harness&Ground
      • If 2 ohm; or greater » Repair the open/high resistance in the circuit.
      • If less than 2 ohm; » Repair the open/high resistance in the ground connection.
    • If less than 10 ohm; 
  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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