U0663 code meaning
Lost Communication With Rear Mode Actuator
What U0663 means
The rear mode actuator steers rear-seat air between upper outlets, such as console or roof vents, and the rear footwell. Hanon's US 11,305,608 shows a dome-shaped rear mode door doing exactly this between console vent and rear floor vent. GM uses the code: bulletin 23-NA-206 lists U0663-00, under GM's own name with the suffix Left, in the body control module of Cadillac, Corvette, Tahoe, Suburban and Yukon models from 2020 or 2021 on, as a history entry caused by software that sets no lamp and can be ignored unless it is current. The added word Left suggests GM may split rear distribution by side. When the link is truly lost, rear passengers get air only from the outlets that were open last, for instance warm air at the face or cold air at the feet.
U0663 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.2 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0663
- No symptom if the code is only stored as history
- Rear air stuck at the console or roof vents or at the floor
- Rear mode button has no effect
Common causes of U0663
- Most likelySoftware timing in the body or climate module storing a false history code (GM)
- PossibleRear mode actuator failed
- Less likelyHarness to the rear HVAC unit or console damaged
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Rear mode actuatorVehicle bus wiring
What each part of U0663 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 63 | The exact fault in that area. |
What to do next
- Note U0663 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0663
What does U0663 mean?
U0663 means "Lost Communication With Rear Mode Actuator". The rear mode actuator steers rear-seat air between upper outlets, such as console or roof vents, and the rear footwell. It is a generic code, so it means the same on every make.
Is it safe to drive with U0663?
U0663 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0663 fail an emissions test?
U0663 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0663 to fix?
Difficulty: hard. A typical repair takes 0.2 to 4 hours of work. This is a job for a workshop.
Will U0663 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.