What it means
Turbocharger or supercharger boost control B is not operating within the expected range or performance limits.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
Boost control B is the actuator circuit and mechanism the engine computer uses to regulate turbocharger or supercharger boost. The computer compares the commanded response of control B with boost and actuator feedback; it sets this code when that response falls outside the expected range or performance.
Common causes
Most likely first.
- Boost control actuator or mechanism fault
- Wiring or connector fault
Symptoms
- Check engine light on
- Reduced engine performance
How to diagnose it
- Record freeze-frame data and compare commanded boost with actual boost and control B feedback to see when the mismatch occurs.
- Inspect the control B actuator, linkage, hoses, and connectors for sticking, damage, disconnection, or corrosion.
- Check the control B wiring for opens, shorts, chafing, and poor terminal contact, especially near hot or moving parts.
- Use a scan tool to command control B, if supported, and observe whether its position or electrical feedback changes smoothly.
- Test the actuator and its circuit against the manufacturer's specification, then check the boost system for leaks or restrictions if the electrical response is sound.
Common fixes
- Reconnect or clean a loose or corroded control B connector.
- Repair damaged wiring or restore the harness routing.
- Repair sticking or damaged control B linkage or mechanism.
- Replace a failed boost control B actuator after confirming the circuit is sound.
Can I keep driving?
Limit acceleration and avoid towing or heavy loads because reduced or unpredictable boost can worsen drivability and may lead to limp mode. If power drops sharply or the engine behaves abnormally, stop in a safe place and have the fault checked.
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.