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DTC codes / U06xx · Network communication / U065F

U065FLost Communication With Left Rear Temperature Actuator A

U065F is a network communication code indicating that a control module on the vehicle's data bus has lost contact with the left rear temperature actuator, which is the small electric motor that moves a blend door to adjust rear cabin temperature. The module that monitors this actuator, typically the rear HVAC control module or the body control module, has stopped receiving expected messages or feedback from the actuator circuit, so it sets this code and may default the rear climate system to a fixed setting.

SystemNetwork
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaNetwork communication

Symptoms you may notice

  • Rear cabin temperature cannot be adjusted, or the rear climate control panel appears unresponsive
  • Air from the rear vents stays stuck on hot or cold regardless of the setting
  • A clicking or humming noise from the rear quarter trim area when the temperature is changed
  • The rear HVAC system may default to a fixed temperature or shut down entirely
  • Often no symptoms besides the warning light, especially if the rear climate control is rarely used

Common causes, most likely first

  1. A failed left rear temperature actuator motor, often due to a worn internal position sensor or stripped gears
  2. A damaged or disconnected electrical connector at the actuator, caused by vibration, moisture, or previous trim work
  3. Broken, chafed, or corroded wiring in the harness between the actuator and the control module
  4. A faulty rear HVAC control module or body control module that is not sending or receiving the communication signal
  5. A binding or jammed rear blend door that overloads the actuator and causes it to drop off the communication bus
  6. Low battery voltage or a weak charging system that disrupts module communication on the data bus
  7. Water intrusion into the rear quarter panel or liftgate area that damages the actuator or its wiring

How to diagnose and fix it

  1. Verify battery voltage and charging system output, then clear the code and test-drive to see if U065F returns
  2. Inspect the actuator connector and wiring for corrosion, loose pins, or physical damage, and repair as needed
  3. Command the left rear temperature actuator through a scan tool bidirectional test to confirm whether it responds and moves the blend door
  4. Remove the actuator and check that the blend door moves freely by hand, repairing a binding door before replacing the motor
  5. Measure resistance and voltage on the actuator control circuit to rule out an open or shorted wire before condemning the actuator
  6. Replace the left rear temperature actuator if it fails the command test or shows an internal fault, then recalibrate the HVAC doors
  7. If the actuator and wiring test good, diagnose the rear HVAC control module or body control module for communication faults on the data bus

Why the actuator often is not the culprit

  • A binding rear blend door frequently mimics a failed actuator by overloading the motor and causing it to drop communication, so always check door movement before replacing parts.
  • The code can be set by a low or failing battery because network communication is voltage-sensitive, and a weak battery may cause this code along with several others.
  • Water leaks into the rear quarter panel or liftgate area are a common hidden cause on vehicles with rear climate control, corroding the actuator connector.
  • A scan tool bidirectional test is the fastest way to separate a dead actuator from a wiring or module problem, and it avoids guessing.
  • This code does not always mean the actuator is bad; a faulty rear HVAC control module or a data bus fault can set the same code.

Can I keep driving with U065F?

The vehicle remains safe to drive because this fault only affects rear cabin temperature comfort and does not impair engine, braking, or steering systems. Avoid repeated attempts to adjust the rear temperature if you hear clicking, and have the circuit inspected soon to prevent further damage to the blend door or actuator.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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