U0663

Lost Communication With Rear Mode Actuator

Moderate severity

The vehicle bus reports loss of communication with smart rear HVAC mode (vent/floor/defrost) actuator. Rear air distribution falls back to a default mode.

Common causes

Bus wiring open or shorted
One of the most commonly reported causes for this code — check this first.
high
Typical part cost: $90-660
Module without power or ground
A plausible cause — test and verify before replacing parts.
medium
Typical part cost: $90-660
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First things to check

1Confirm the code with a scan tool and check for additional related codes.
2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.

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Related codes

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Frequently asked questions

What does U0663 mean?

U0663 means "Lost Communication With Rear Mode Actuator". It is a generic OBD-II code that points to a fault in the network / communication.

What are the most common causes of U0663?

bus wiring open or shorted; module without power or ground; module failed — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.

Can I keep driving with this code?

The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.

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