Hands Free Module (HFM)

B143E-MICROPHONE 2 CIRCUIT LOW





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

Theory of Operation

The Hands Free Module (HFM) controls and monitors the (X722) microphone 2 input circuit (+) for a concern. The microphone is located in the rearview mirror.

For a detailed description of the Hands Free System. Navigation/Telecommunication - Description.

For additional information regarding the operation of the Hands Free System. Navigation/Telecommunication - Operation.

- When Monitored:
With the ignition on.

- Set Condition:
The Hands Free Module (HFM) detects a short to ground or an open on the (X722) Microphone 2 IN (+) circuit.





1. CHECK FOR 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 B143E-MICROPHONE 2 CIRCUIT LOW 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 (X793) MICROPHONE FEED CIRCUIT FOR AN OPEN




1. Turn the ignition off.
2. Disconnect the Inside Rearview Mirror harness connector.
3. Turn the ignition on.
4. Measure the voltage between the (X793) Microphone Feed circuit and ground.

Is the voltage above 10.0 volts?

Yes

- Go To 3

No

- Repair the (X793) Microphone Feed circuit for an open or a short to ground.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

3. CHECK THE INSIDE REARVIEW MIRROR




1. Turn the ignition off.
2. Connect a jumper wire between the (X793) Microphone Feed and the (X722) Microphone 2 IN (+) circuits.
3. Turn the ignition on.
4. With the scan tool, read the DTCs.

NOTE: DTC B143F-MICROPHONE 2 CIRCUIT HIGH should display as active as a result of this test.

Does the scan tool display B143E-MICROPHONE 2 CIRCUIT LOW as active?

Yes

- Go To 4

No

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

4. CHECK THE (X722) MICROPHONE 2 IN (+) CIRCUIT FOR AN OPEN




1. Turn the ignition off.
2. Disconnect the Hands Free Module harness connector.
3. Measure the resistance of the (X722) Microphone 2 IN (+) circuit between the Inside Rearview Mirror and Hands Free Module harness connectors.

Is the resistance above 10K Ohms?

Yes

- Repair the (X722) Microphone 2 IN (+) circuit for an open.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

No

- Go To 5

5. CHECK THE (X722) MICROPHONE 2 IN (+) CIRCUIT FOR A SHORT TO GROUND




1. Measure the resistance between ground and the (X722) Microphone 2 IN (+) circuit.

Is the resistance below 10K Ohms?

Yes

- Repair the (X722) Microphone 2 IN (+) circuit for short to ground.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

No

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