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U065F Lost Communication With Left Rear Temperature Actuator A

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Vehicles with a separately controlled rear climate zone need their own temperature doors for the rear outlets, and in a split rear system the left side may use two of them, labelled A and B. Hanon's US 11,305,608 shows why two can be needed: one door ahead of the heater core and a second behind it mixing warm air into the rear cold-air duct. Which door counts as A is up to the maker. GM uses this code: bulletin 23-NA-206 lists U065F-00 in the body control module of the CT4, CT5, Corvette, Escalade, Tahoe, Suburban and Yukon from model year 2020 or 2021 on as a history code from software anomalies that turns on no lamp and may be ignored; if it is current, normal diagnosis applies. A real loss leaves the rear left air at one temperature.

Likely causes

Software timing between modules logs a false history code (GM)
Left rear temperature actuator A failed
Rear HVAC harness or connector damaged in the floor or rear quarter

Symptoms

  • Often none when the code is only stored as history
  • Rear left air stays hot or cold
  • Rear temperature control has no effect on the left

Repair estimate

DifficultyHardWorkshop job
Parts and labour€0–600
Time0.2–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

lr temp actuator avehicle bus wiring

Related codes

U0660U0661U0663U0164

References: static.nhtsa.gov, patents.google.com, en.wikipedia.org.