• 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.

The radio provides the cellular phone microphone with a supplied voltage on the cellular phone microphone high signal circuit. When the microphone is in use, voice data from the user is sent back to the radio on the cellular microphone low signal circuit.

• The ignition must be in the RUN or ACC position/vehicle in Service Mode.
• The system voltage is at least 9.5 V and no more than 15.5 V.
• All the above conditions are present for greater than 10 s.

The radio detects a short to ground in the cellular phone microphone high signal circuit for 10 s or greater.

The following conditions will set this DTC:

• The radio detects an open/high resistance in the cellular phone microphone high signal circuit for 10 s or greater.
• The radio detects an open/high resistance in the microphone low signal circuit for 10 s or greater.

• The radio will not receive a signal from the cellular phone microphone.
• Calls can be placed but the caller cannot be heard.

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.

Radio/Navigation System Schematics

Master Electrical Component List

Radio/Audio System Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

1. Ignition OFF/vehicle OFF, disconnect the harness connector at the B24LF Mobile Telephone Microphone – Left Front, ignition ON/vehicle in Service Mode.
2. Test for 8.5-9.5 V between the signal circuit terminal B and ground.
• If less than 8.5 V
1. Ignition OFF/vehicle OFF, disconnect the X2 harness connector at the A11 Radio.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground in the circuit.
• If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the A11 Radio.
• If greater than 9.5 V
1. Ignition OFF/vehicle OFF, disconnect the X2 harness connector at the A11 Radio .
2. Ignition ON/vehicle in Service Mode, test for less than 1 V between the signal circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the A11 Radio .
• If between 8.5-9.5 V
3. Test for less than 1 V between the low reference circuit terminal A and ground.
• If greater than 1 V
1. Ignition OFF/vehicle OFF, disconnect the X2 harness connector at the A11 Radio .
2. Ignition ON/vehicle in Service Mode, test for less than 1 V between the low reference circuit and ground.
• If 1 V or greater, repair the short to voltage in the circuit.
• If less than 1 V, replace the A11 Radio
• If less than 1 V
4. Test for greater than 8.5 V between the signal circuit terminal B and the low reference circuit terminal A.
• If less than 8.5 V
1. Ignition OFF/vehicle OFF, disconnect the X2 harness connector at the A11 Radio.
2. Test for infinite resistance between the low reference circuit and ground.
• If less than infinite resistance, repair the short to ground in the circuit.
• If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the A11 Radio.
• If greater than 8.5 V
5. Test or replace the B24LF Mobile Telephone Microphone – Left Front.

Perform the Diagnostic Repair Verification after completing the repair.

• Mobile Telephone Microphone Replacement
• Control Module References for telematics communication interface control module replacement, programming and setup.