DTC B1274 or B137B-B137D
Cellular, Entertainment, and Navigation | Diagnostic Information and Procedures | Document ID: 5882934 Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provide an overview of each diagnostic category. DTC Descriptors DTC B137B Noise Reduction Microphone 1 Signal DTC B137C Noise Reduction Microphone 2 Signal DTC B137D Noise Reduction Microphone 3 Signal For symptom byte information refer to Symptom Byte List Diagnostic Fault Information
| Circuit | Circuit Function | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performan |
|---|---|---|---|---|---|
| 3005 | Signal | B137B 11 | B137B 13 | B137B 12 | B137B 28 |
| 3008 | Signal | B137B 11 | B137B 13 | B137B 12 | B137B 28 |
| 3006 | Signal | B137C 11 | B137C 13 | B137C 12 | B137C 28 |
| 3009 | Signal | B137C 11 | B137C 13 | B137C 12 | B137C 28 |
| 3007 | Signal | B137D 11 | B137D 13 | B137D 12 | B137D 28 |
| 3010 | Signal | B137D 11 | B137D 13 | B137D 12 | B137D 28 |
Circuit/System Description The active noise cancellation system uses three microphones in the vehicle headliner: one above each front seating position, and one above the rear seat. The T3 Audio Amplifier provides a bias voltage to each microphone (+) and (-) signal circuits for operation of the microphone. The microphones monitor the vehicle cabin for undesirable engine sounds. The Audio Amplifier uses the microphone inputs and an engine RPM signal to determine the frequency of the undesirable sound. Conditions for Running the DTC The T3 Audio Amplifier performs a self diagnostic of the microphone circuits 16 seconds after initial power up, then periodically every 400 milliseconds thereafter. Conditions for Setting the DTC DTC B137B 12, B137C 12, B137D 12 DTC B1325 is not current A short to voltage is detected on the specified (+) or (−) signal circuit for more than 1.5 seconds DTC B137B 11, B137C 11, B137D 11 DTC B1325 is not current A short to ground is detected on the specified (+) or (−) signal circuit for more than 1.5 seconds DTC B137B 13, B137C 13, B137D 13 DTC B1325 is not current An open is detected on the specified (+) or (−) signal circuit for more than 1.5 seconds DTC B137B 28, B137C 28, B137D 28 DTC B1325 is not current An out of range voltage is detected on the specified (+) or (−) signal circuit for more than 1.5 seconds. Action Taken When the DTC Sets The active noise cancellation system is disabled. Conditions for Clearing the DTC A current DTC clears when the self diagnostic passes on the next ignition cycle. A history DTC clears when the ignition cycle counter reaches the reset threshold without a repeat of the malfunction. Diagnostic Aids Installation of aftermarket replacement speakers, additional speakers/subwoofers, or aftermarket exhaust systems can cause undesirable behavior of the active noise cancellation system. The noise reduction microphones have foam blocks above them to seal the microphones and aid in the reduction of headliner vibration. Missing or out of place foam blocks can impact system performance. Reference Information Schematic Reference Radio/Navigation System Schematics Connector End View Reference Master Electrical Component List Description and Operation Active Noise Cancellation Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Testing
- 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 3.1. 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. ⇓ If a short to ground is not found 3.2. 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. ⇓ If an open/high resistance is not found 3.3. Replace the T3 Audio Amplifier ⇒ If greater than 8.5 V 3.1. 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. ⇓ If a short to voltage is not found 3.2. Replace the T3 Audio Amplifier ⇓ 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 4.1. 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. ⇓ If a short to ground is not found 4.2. 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. ⇓ If an open/high resistance is not found 4.3. Replace the T3 Audio Amplifier ⇒ If greater than 7 V 4.1. 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. ⇓ If a short to voltage is not found 4.2. Replace the T3 Audio Amplifier ⇓ 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 ⇓ If the DTC does not set
- All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Communication Interface Module Microphone Replacement Active Noise Cancellation Microphone Replacement Control Module References for Audio Amplifier replacement, programming, and setup.