What it means
During cold-start monitoring, the control module detects that boost control A is not performing as expected.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Boost control A regulates turbocharger or supercharger pressure during the monitored cold-start period; the exact actuator or valve represented by A depends on the vehicle. The engine control module compares commanded boost control with the measured response and sets this code when control A does not perform as expected while cold.
Common causes
Most likely first.
- Turbocharger or supercharger boost actuator sticking when cold
- Boost control valve or solenoid fault
- Vacuum hose leak or restriction, if fitted
- Wiring or connector fault affecting boost control
Symptoms
- Check-engine light may come on
- Reduced power or poor acceleration, especially during cold start
How to diagnose it
- Read freeze-frame data and note coolant temperature, engine load, and boost readings when the fault set; confirm whether the event occurred during a cold start.
- On a cold engine, use a scan tool to compare commanded and actual boost-control A operation during the conditions specified by the manufacturer.
- Inspect the boost-control A actuator, valve or solenoid, electrical connector, and harness for damage, sticking, or corrosion.
- Check any vacuum hoses serving boost control A for leaks, kinks, disconnection, or restriction, if the system uses them.
- Test the A circuit, actuator movement, and boost response against the manufacturer's specification before considering turbocharger or supercharger replacement.
Common fixes
- Reconnect a loose boost-control A connector or secure a disconnected hose.
- Repair a leaking, kinked, or restricted vacuum hose if fitted.
- Repair damaged wiring or corroded terminals in the A control circuit.
- Replace a faulty boost-control A solenoid or valve.
- Repair or replace a sticking actuator or other confirmed mechanical boost-control fault.
Can I keep driving?
If power is reduced, avoid hard acceleration, towing, and situations that require rapid merging until the cold-start boost fault is diagnosed. Stop driving if the engine develops severe power loss, unusual turbo noise, or other signs of a serious mechanical problem.
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.