U065B: Lost Communication With Left Front Mode Actuator

What it means

A control module has stopped receiving expected network messages from the left front mode actuator. The effect on air distribution depends on the vehicle's HVAC design.

How it works

The left front mode actuator moves the HVAC doors that direct air to outlets such as the dash vents, floor, and windshield. U065B sets when a control module stops receiving its expected messages from that actuator, so air may not reach the selected outlets.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Warning light or message related to the HVAC system
• Air may not be directed to the selected outlets

How to diagnose it

1. Scan the HVAC and other modules for freeze-frame data and related communication faults to determine whether the left front mode actuator is the only device offline.
2. Select vent, floor, and defrost modes and note whether airflow changes at the left front outlets or scan-tool data shows actuator movement.
3. Inspect the left front mode actuator connector and harness for looseness, corrosion, chafing, or damage around the HVAC case.
4. Check the actuator's specified power and ground, as a missing supply can prevent network communication.
5. Test the actuator's network wiring for opens, shorts, and poor connections to the manufacturer's specification before following the vehicle's actuator diagnosis procedure.

Common fixes

• Reconnect or secure the left front mode actuator connector.
• Repair damaged wiring or corroded connector terminals at the actuator.
• Restore a missing actuator power or ground supply after correcting the cause.
• Replace the left front mode actuator or its module if testing verifies an internal failure.

Can I keep driving?

You can usually drive if the only effect is that left front airflow stays in the wrong mode. Do not drive if the system cannot direct enough air to the windshield to maintain clear visibility.