U02ACLost Communication With Turbocharger/Supercharger Boost Control A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Check engine lamp
- Noticeably less boost and power, engine in reduced-power mode
- Boost actuator values missing or frozen in the scan tool
- Likely causes
- LikelyCorroded or loose actuator connector, chafed bus wires near the hot turbocharger
- PossibleActuator loses its supply or ground (fuse, relay, ground point)
- PossibleElectronics inside the boost actuator failed, often from heat
- RareWeak 12 V battery causing modules to drop off during cranking
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €50 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.