B1427
DTC B1427 (2-6): Microphone Circuit Malfunction1. Delete the DTCs.
2. Turn the ignition switch OFF, and then back ON (II).
3. Check for DTCs.
Is DTC B1427 (2-6) indicated?
YES - Go to step 4.
NO - Intermittent failure. The system is OK at this time. Check for loose or poor connections.
4. Turn the ignition switch OFF.
5. Disconnect OnStar control unit connector B (16P).
6. Disconnect the roof console 28P connector.
7. Connect roof console 28P connector terminals No. 3 and No. 4 to body ground with jumper wires.
8. Check for continuity between body ground and OnStar control unit connector B (16P) terminals No. 1 and No. 9 individually.
Is there continuity?
YES - Go to step 9.
NO - Repair an open in the wire.
9. Remove the jumper wires from the roof console.
10. Check for continuity between body ground and OnStar control unit connector B (16P) terminals No. 1 and No. 9 individually.
Is there continuity?
YES - Repair a short to ground in the wire.
NO - Go to step 11.
11. Turn the ignition switch ON (II).
12. Measure voltage between body ground and OnStar control unit connector B (16P) terminals No. 1 and No. 9 individually.
Is there voltage?
YES - Repair a short to power in the wire.
NO - Go to step 13.
13. Reconnect OnStar control unit connector B (16P).
14. Measure voltage between OnStar control unit connector B (16P) terminals No. 1 and No. 9.
Is there about 8.5 V?
YES - Substitute a known-good microphone and recheck. If the DTC B1427 (2-6) is indicated again, replace the OnStar control unit.
NO - Replace the OnStar control unit.