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U02AC Lost Communication With Turbocharger/Supercharger Boost Control A

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Boost control A is the actuator that sets boost, usually a vane or wastegate drive with its own electronics that receives targets and reports status over a data link. U02AC means the engine controller has stopped hearing from it. No manufacturer documents U02AC publicly. GM files the same situation under U010C: its 2025 tables flag the Turbocharger Boost Control Module when frame $099 is missing for over 10 s or $499 for over 9.2 s, with battery above 11 V and the bus itself healthy, and rate it Type B (lamp after two trips). CARB requires boost actuators to be monitored and a lost digital link to carry its own code. Ford's patent on an electric wastegate shows the fallback: a spring keeps the valve closed. Expect a warning lamp and reduced power.

Likely causes

Corroded or loose actuator connector, chafed bus wires near the hot turbocharger
Actuator loses its supply or ground (fuse, relay, ground point)
Electronics inside the boost actuator failed, often from heat
Weak 12 V battery causing modules to drop off during cranking

Symptoms

  • Check engine lamp
  • Noticeably less boost and power, engine in reduced-power mode
  • Boost actuator values missing or frozen in the scan tool

Repair estimate

DifficultyHardWorkshop job
Parts and labour€50–2,500
Time0.5–5 h

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

Parts involved

boost control module avehicle bus wiring

Related codes

U02ADU010CU0656P00AFP0045

References: law.cornell.edu, gsi.ext.gm.com, patents.google.com.