Hands Free Module (HFM)

B143A-13-MICROPHONE 1 - CIRCUIT OPEN





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Hands Free Module (HFM) controls and monitors both the (X712) microphone 1 input circuit (+) and the (X792) microphone 1 input circuit (-) for a concern. The HFM communicates over the CAN-AT Bus. The microphone is located in the rearview mirror.

For a detailed description of the Hands Free System. Hands Free Module - Description.

For additional information regarding the operation of the Hands Free System. Hands Free Module - Operation.

- When Monitored:
With the ignition on.

- Set Condition:
The HFM detects an open on either the (X712) Microphone 1 IN (+) circuit or the (X792) Microphone 1 IN (-) circuit for greater than 10 seconds.





1. CHECK FOR AN ACTIVE DTC

NOTE: Verify the connection of the Rearview Mirror harness connector.

1. Turn the ignition on.
2. With the scan tool, read the active DTCs.

Does the scan tool display: B143A-13-MICROPHONE 1 - CIRCUIT OPEN as active?

Yes

- Go To 2

No

- Test complete, the condition or conditions that originally set this DTC are not present at this time. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals and correct pin tension.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

2. CHECK THE INSIDE REARVIEW MIRROR




1. Turn the ignition off.
2. Disconnect the Inside Rearview Mirror harness connector
3. Connect a jumper wire between the (X792) Microphone 1 IN (-) and the (X712) Microphone 1 IN (+) circuits.
4. Turn the ignition on.
5. With the scan tool, read the DTCs.

NOTE: B143A-92-MICROPHONE 1 - PERFORMANCE OR INCORRECT OPERATION should display as active as a result of this test.

Does the scan tool display: B143A-13-MICROPHONE 1 - CIRCUIT OPEN as active?

Yes

- Go To 3

No

- Replace the Inside Rearview Mirror.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

3. CHECK THE (X712) MICROPHONE 1 IN (+) CIRCUIT FOR AN OPEN




1. Turn the ignition off.
2. Disconnect the Hands Free Module harness connector.
3. Measure the resistance of the (X712) Microphone 1 IN (+) circuit between the Inside Rearview Mirror and Hands Free Module harness connectors.

Is the resistance below 5.0 Ohms?

Yes

- Go To 4

No

- Repair the (X712) Microphone 1 IN (+) circuit for an open.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

4. CHECK THE (X792) MICROPHONE 1 IN (-) CIRCUIT FOR AN OPEN




1. Measure the resistance of the (X792) Microphone 1 IN (-) circuit between the Inside Rearview Mirror and Hands Free Module harness connectors.

Is the resistance below 5.0 Ohms?

Yes

- Replace the Hands Free Module. Hands Free Module - Removal.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

No

- Repair the (X792) Microphone 1 IN (-) circuit for an open.
- Perform the BODY VERIFICATION TEST. Body Verification Test.