What it means
The vehicle bus reports loss of communication with boost control module B (electric wastegate or VTG actuator). Boost pressure cannot be commanded; the engine reverts to a low-power fallback.
At a glance
- Usually lights the warning light of the system that lost communication
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
Boost control module B operates the electric wastegate or variable-geometry turbo actuator and reports its status over the vehicle network. The engine controller monitors messages from this module; U02AD sets when those messages stop arriving, preventing reliable boost commands through channel B.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan all modules for network codes and freeze-frame data to see whether U02AD appeared with a wider communication or power-supply fault.
- Check live data for boost control B communication and commanded status, and compare it with any available boost control A data.
- Inspect module B's connector and nearby bus wiring for looseness, corrosion, damage, or signs of water entry.
- Check the module B power and ground circuits under the conditions specified by the manufacturer.
- Test the network wiring to module B for an open, short, or poor connection using the manufacturer's procedure.
- If wiring, power, and ground pass, follow the manufacturer's checks to determine whether boost control module B has failed.
Common fixes
- Reconnect or clean a loose or corroded module B connector.
- Repair damaged bus wiring or a poor connection to boost control B.
- Restore the module's power or ground supply.
- Replace boost control module B if testing confirms it has failed.
Can I keep driving?
Reduced engine power or limp mode may make merging and overtaking difficult. Avoid hard acceleration and towing, and stop somewhere safe if power loss is severe or other engine warnings appear.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.