What it means
The turbocharger or supercharger boost control A circuit is reporting voltage above the expected range.
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 A is the circuit the module uses to command the turbocharger or supercharger boost-control actuator or solenoid. The module monitors circuit voltage as it controls boost. P0048 sets when Boost Control A voltage is higher than expected, which can result from a short to battery voltage or a wire contacting a powered source.
Common causes
Most likely first.
- Wiring shorted to battery
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Reduced engine performance
How to diagnose it
- Review freeze-frame data and live boost-control readings to establish when Boost Control A voltage went high.
- Inspect the Boost Control A harness for pinching, heat damage, exposed conductors, or contact with battery-voltage wiring.
- Use the wiring diagram to identify the circuit pins and check for voltage where the manufacturer's procedure says none should be present.
- Test the Boost Control A circuit for a short to battery voltage and inspect connector pins for corrosion or poor contact.
- If wiring checks pass, test the actuator or solenoid and verify module control using the manufacturer's diagnostic procedure.
Common fixes
- Repair Boost Control A wiring that is shorted to battery voltage.
- Reroute or secure pinched wiring away from powered circuits and hot components.
- Repair corroded or damaged connector terminals.
- Replace the Boost Control A actuator or solenoid if it fails the specified test.
Can I keep driving?
The fault can cause reduced power or limp mode, so avoid towing and hard acceleration and leave room for slower acceleration in traffic. Stop safely if the engine loses power sharply or develops smoke or unusual turbo noise.
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.