Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

Ignition OFF, disconnect the appropriate B312 Active Noise Cancellation Microphone(s):
- DTC B137B = B312 Active Noise Cancellation Microphone(s) connected to circuit 3005
- DTC B137C = B312 Active Noise Cancellation Microphone(s) connected to circuit 3006
- DTC B137D = B312 Active Noise Cancellation Microphone(s) connected to circuit 3007
Ignition ON.
Test for 6.5 - 8.5 V between the signal circuit terminal 2 and ground.
- If less than 6.5 V
1. Test the appropriate circuit for a short to ground:
  - DTC B137B = Circuit 3005
  - DTC B137C = Circuit 3006
  - DTC B137D = Circuit 3007
  - If a short to ground is found, repair the circuit fault.
  - Go to next step: If a short to ground is not found
2. Test the appropriate circuit for an open/high resistance:
  - DTC B137B = Circuit 3005
  - DTC B137C = Circuit 3006
  - DTC B137D = Circuit 3007
  - If an open/high resistance is found, repair the circuit fault.
  - Go to next step: If an open/high resistance is not found
3. Replace the T3 Audio Amplifier
- If greater than 8.5 V
1. Test the appropriate circuit for a short to voltage:
  - DTC B137B = Circuit 3005
  - DTC B137C = Circuit 3006
  - DTC B137D = Circuit 3007
  - If a short to voltage is found, repair the circuit fault.
  - Go to next step: If a short to voltage is not found
2. Replace the T3 Audio Amplifier
- Go to next step: If between 6.5 - 8.5 V
Test for 6.5 - 8.5 V between the signal circuit terminal 1 and ground.
- If less than 6.5 V
1. Test the appropriate circuit for a short to ground:
  - DTC B137B = Circuit 3008
  - DTC B137C = Circuit 3009
  - DTC B137D = Circuit 3010
  - If a short to ground is found, repair the circuit fault.
  - Go to next step: If a short to ground is not found
2. Test the appropriate circuit for an open/high resistance:
  - DTC B137B = Circuit 3008
  - DTC B137C = Circuit 3009
  - DTC B137D = Circuit 3010
  - If an open/high resistance is found, repair the circuit fault.
  - Go to next step: If an open/high resistance is not found
3. Replace the T3 Audio Amplifier
- If greater than 7 V
1. Test the appropriate circuit for a short to voltage:
  - DTC B137B = Circuit 3008
  - DTC B137C = Circuit 3009
  - DTC B137D = Circuit 3010
  - If a short to voltage is found, repair the circuit fault.
  - Go to next step: If a short to voltage is not found
2. Replace the T3 Audio Amplifier
- Go to next step: If between 6.5 - 8.5 V
Replace the B312 Active Noise Cancellation Microphone.
Ignition ON
Verify the DTC does NOT set.
- If the DTC sets
  Replace the T3 Audio Amplifier
- Go to next step: If the DTC does not set
All OK.