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U0662 Lost Communication With Right Rear Temperature Actuator B

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

With four rear temperature actuators, A and B on each side, plus front units, a climate system may run many look-alike motors on LIN, where one master serves up to 15 slaves. Identical parts must be told apart, either by part variant or by position detection along a daisy chain, as the LIN article explains. That makes right rear actuator B prone to a specific trap: a new or swapped unit that was never assigned its address answers on the wrong identifier, and the master logs U0662 although the part works. No maker documents this code publicly. A genuine loss only affects the fine mixing on the right rear side; actuator A keeps basic control there. Chips such as NXP's MM908E626 show the usual three-wire hookup of supply, ground and LIN.

Likely causes

Replacement or swapped actuator B without the correct LIN address
Actuator B electronics failed
Open supply, ground or LIN pin at actuator B

Symptoms

  • Right rear temperature imprecise or slow to settle
  • Code appears right after an actuator was replaced

Repair estimate

DifficultyHardWorkshop job
Parts and labour€0–600
Time0.5–4 h

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

Parts involved

rr temp actuator bvehicle bus wiring

Related codes

U0661U0660U0164

References: en.wikipedia.org, nxp.com, patents.google.com.