Microphone Inoperative - Caller Cannot Be Heard

Step	Action	Value(s)	Yes	No
Schematic Reference: OnStar Schematics DEFINITION: The OnStar® call center operator can clearly be heard but will advise the caller that they can not clearly hear them or can not hear them at all.
1	Did you perform the Cellular Communication Diagnostic System Check?	-	Go to Step 2	Go to Diagnostic System Check - Cellular Communication
2	Turn ON the ignition, with the engine OFF. Press the OnStar® call center button. Ask the OnStar® operator if your voice can clearly be heard. Does the OnStar® operator hear your voice?	-	Go to TESTING FOR INTERMITTENT AND POOR CONNECTIONS	Go to Step 3
3	Turn OFF the ignition. Disconnect the OnStar® Microphone. Turn ON the ignition, with the engine OFF. Measure the voltage from the Cellular Telephone Microphone Signal circuit to a good ground. Does the voltage measure near the specified value?	9 V	Go to Step 4	Go to Step 5
4	Measure the voltage from the Cellular Telephone Microphone Signal circuit to the drain wire. Does the voltage measure near the specified value?	9 V	Go to Step 7	Go to Step 6
5	Test the Cellular Telephone Microphone Signal circuit for an open or a short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition?	-	Go to Step 14	Go to Step 8
6	Test the Drain Wire for an open. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition?	-	Go to Step 14	Go to Step 11
7	Test the drain wire circuit for a short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition?	-	Go to Step 14	Go to Step 9
8	Leave the microphone disconnected. Disconnect the VIU connector C1. Test the cellular telephone microphone signal circuit and drain wire circuit for a short together. Did you find and correct the condition?	-	Go to Step 14	Go to Step 9
9	Test the microphone signal circuit between the VIU and VCU for an open or short to ground. Did you find and correct the condition?	-	Go to Step 14	Go to Step 10
10	Inspect for poor connections at the harness connector of the Microphone assembly. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS . Did you find and correct the condition?	-	Go to Step 14	Go to Step 13
11	Inspect for poor connections at the harness connector of the VIU. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS . Did you find and correct the condition?	-	Go to Step 14	Go to Step 12
12	Replace the Microphone assembly. Refer to OnStar Microphone Replacement . Did you complete the replacement?	-	Go to Step 14	-
13	IMPORTANT: Perform the OnStar® setup procedure. Replace the VIU. Refer to OnStar Vehicle Interface Unit (VIU) Replacement .Did you complete the replacement?	-	Go to Step 14	-
14	Operate the system in order to verify the repair. Did you correct the condition?	-	System OK	Go to Step 2