Sorry, the NHTSA has not posted this TSB document yet.
You can still get the detailed info from Chevrolet for this TSB. Call your local Chevrolet dealer's service department & ask for a copy of TSB# GCUS-3-424.
15663A - SERVICE UPDATE (REVISED SPECIAL REPAIR TOOL ADDED). RELOCATE A WIRE CIRCUIT WITHIN THE ONSTAR CONNECTOR. THESE VEHICLES LACK A GROUND IN THE MICROPHONE RETURN PATH, WHICH RESULTS IN THE VOICE RECOGNITION BECOMING INOPERABLE WHEN THE VEHICLE IS IN RETAINED ACCESSORY (RAP) OR ACCESSORY POWER MODE. IN ADDITION, THE HANDS-FREE VOICE QUALITY CAN BE DEGRADED. THE ONSTAR FUNCTIONS ARE NOT IMPACTED BY THIS CONDITION.
