What it means
Supply voltage feeding boost control actuator B is above the expected range. Likely charging system overvoltage or wiring shorted to a higher potential.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The boost control actuator's B supply circuit provides power to the actuator that helps regulate turbocharger or supercharger boost. The engine control module monitors that supply and sets P005F when its voltage is higher than the expected range, which can happen if the charging system overcharges or the wiring contacts a higher-voltage source.
Common causes
Most likely first.
- Alternator regulator failed (overvoltage)
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Reduced engine power or acceleration, if boost control is affected
How to diagnose it
- Use a scan tool to record freeze-frame data and check charging-system voltage, since system-wide overvoltage can affect the actuator supply.
- Inspect the boost control actuator B connector and nearby harness for corrosion, pin damage, pinching, or contact with a B+ wire.
- Check the charging system against the manufacturer's specification to see whether the alternator regulator is raising voltage excessively.
- With the wiring diagram, check actuator B supply voltage and continuity for an unintended connection to a higher-potential circuit.
- If the supply and harness check out, test the actuator circuit and control module using the manufacturer's diagnostic procedure.
Common fixes
- Repair a pinched or chafed actuator B supply wire that is touching a B+ source.
- Clean or repair corroded or damaged connector terminals.
- Repair or replace the alternator or regulator if charging voltage is above the manufacturer's specification.
- Repair the boost control actuator B circuit or replace a confirmed faulty actuator.
Can I keep driving?
If power is reduced or the vehicle enters limp mode, avoid hard acceleration and towing; boost control may be limited. Arrange diagnosis soon, since reduced power can make merging or passing unsafe.
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.