U02AC code meaning
Lost Communication With Turbocharger/Supercharger Boost Control A
Network system Generic code U02xx codes Check engine light
What U02AC means
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.
U02AC at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 5 hours
- Clears after repairAfter a drive cycle
Symptoms of U02AC
- Check engine lamp
- Noticeably less boost and power, engine in reduced-power mode
- Boost actuator values missing or frozen in the scan tool
Common causes of U02AC
- Most 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
- Less likelyWeak 12 V battery causing modules to drop off during cranking
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Boost control module aVehicle bus wiring
What each part of U02AC means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| AC | The exact fault in that area. |
What to do next
- Note U02AC 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 U02AC
What does U02AC mean?
U02AC means "Lost Communication With Turbocharger/Supercharger Boost Control A". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with U02AC?
Drive gently and only to a workshop. With U02AC the car can go into limp mode (reduced power) to protect itself.
Will U02AC fail an emissions test?
Yes, it can. U02AC is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U02AC to fix?
Difficulty: hard. A typical repair takes 0.5 to 5 hours of work. This is a job for a workshop.
Will U02AC clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.