What it means
A control module has stopped receiving expected network messages from the left front temperature actuator. The effect on cabin temperature control depends on the vehicle's HVAC design.
How it works
The left front temperature actuator adjusts the blend of heated and cooled air for the left front HVAC zone. U0659 sets when a control module stops receiving its expected network messages, so the left front temperature door may not follow the driver's setting.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
Symptoms
- Warning light or message related to the HVAC system
- Left front air temperature may not respond as commanded
How to diagnose it
- Scan the HVAC and other modules for freeze-frame data and related communication faults, noting whether the fault is limited to the left front temperature actuator.
- Command a range of left front temperature settings and observe whether the air temperature changes or the actuator appears in scan-tool data.
- Inspect the left front temperature actuator connector and harness for loose or damaged terminals, chafing, or obstruction around the actuator.
- Check the actuator's specified power and ground, since a loss of either can prevent it from communicating.
- Test the actuator's network wiring for opens, shorts, and poor connections to the manufacturer's specification, then follow the vehicle's diagnostic procedure if the circuit is sound.
Common fixes
- Reconnect or secure the left front temperature actuator connector.
- Repair damaged or corroded wiring and terminals at the left front actuator.
- Restore a missing power or ground supply after correcting its cause.
- Replace the left front temperature actuator or its module if testing confirms it has failed.
Can I keep driving?
You can generally drive if the HVAC fault is limited to left front temperature control. If the system cannot clear the windshield or keep the cabin comfortable enough for safe driving, stop and address the visibility or comfort problem before continuing.
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.