What it means
The vehicle bus reports loss of communication with smart left-rear HVAC temperature blend door actuator A. Rear-left air temperature falls back to a default position.
How it works
Left rear temperature actuator A controls a rear HVAC blend door that adjusts air temperature for the left rear area. U065F sets when a control module stops receiving expected network messages from actuator A, so left rear temperature may stay at its default position or stop following adjustments.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan HVAC modules for freeze-frame data and related communication faults, confirming whether left rear temperature actuator A is the missing device.
- Change the left rear temperature setting and check for an air-temperature response or a change in actuator A data on the scan tool.
- Inspect actuator A's connector and harness in the left rear HVAC area for loose pins, corrosion, chafing, or damage.
- Check actuator A's specified power and ground, since either loss can stop network communication.
- Test its network wiring for opens, shorts, and poor connections to the manufacturer's specification, then follow the vehicle's actuator diagnosis procedure.
Common fixes
- Reconnect or secure left rear temperature actuator A's connector.
- Repair damaged wiring or corroded terminals at actuator A.
- Restore actuator A's power or ground after correcting the supply fault.
- Replace left rear temperature actuator A or its module if testing confirms an internal failure.
Can I keep driving?
You can generally drive if the fault is limited to left rear cabin temperature control. Check that the front HVAC still provides adequate comfort and windshield clearing.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.