What it means
The vehicle bus reports loss of communication with smart right-rear HVAC temperature blend door actuator B. Rear-right air temperature falls back to a default position.
How it works
The right-rear temperature actuator B is a smart HVAC component that positions a blend door for rear-right air temperature control. U0662 sets when the vehicle network stops receiving messages from actuator B, and the affected temperature function may fall back to a default position.
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 all modules for network faults and review freeze-frame or event data to determine whether U0662 began alongside other communication codes or a low-voltage event.
- Check HVAC live data for right-rear temperature actuator B and command a temperature change to see whether its reported status or position responds.
- Inspect actuator B's connector and right-rear harness for loose terminals, corrosion, moisture, abrasion, or pinched wires.
- Measure actuator B's specified power and ground, including under load, to rule out a supply fault.
- Test the network circuit serving actuator B for opens, shorts, or abnormal resistance according to the wiring diagram and manufacturer procedure.
- If its power, ground, and network circuit are sound, perform the manufacturer's communication test before considering actuator B replacement.
Common fixes
- Reconnect and secure the right-rear temperature actuator B connector.
- Repair chafed, corroded, or broken wiring at actuator B.
- Restore the actuator's failed power or ground connection.
- Repair a network open or short affecting actuator B.
- Replace actuator B after its power, ground, and bus wiring have passed testing.
Can I keep driving?
Driving is generally possible because the fault is limited to rear-right temperature control, but that area may not reach the requested temperature. Avoid relying on the rear HVAC to keep occupants comfortable until it is repaired, and investigate promptly if other systems report communication faults.
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.