Fuel and air

P0048 — Turbo/Supercharger Boost Control "A" Circuit High

Severity: medium Drive with care, to a shop

What P0048 means

The engine control module regulates boost pressure through a control circuit, usually driving a solenoid that operates the wastegate or variable-geometry vanes. P0048 sets when the voltage in circuit "A" is higher than expected, for example from a short to voltage or an open circuit. The ECM then can't control boost accurately.

Symptoms

  • Check Engine light on
  • Reduced power and sluggish acceleration
  • Erratic or unstable boost pressure
  • Whistling or hissing from the turbo area
  • Limp mode under load

Possible causes

  1. Failed boost control solenoid
  2. Damaged wiring: short to voltage, corrosion or loose connector pins
  3. Vacuum leaks or damaged hoses at the control valve
  4. Stuck or failed wastegate, actuator or variable-geometry mechanism
  5. ECM software problem or internal fault (rare)

How to diagnose

  1. Scan for codes and freeze frame data, clear the code and see if it returns
  2. Inspect the wiring and connector at the boost control solenoid for chafing, corrosion and a poor fit
  3. Check for power and ground at the connector and test the signal wire for a short to voltage
  4. Measure the solenoid coil resistance and compare it with the spec
  5. Inspect vacuum hoses and lines for cracks, leaks and kinks
  6. Check charge-air hoses and intercooler connections for leaks
  7. Compare commanded and actual boost pressure in live data
  8. Check that the wastegate or variable-geometry mechanism moves freely

Common fixes

  • Replace the boost control solenoid
  • Repair or replace damaged wiring and connectors
  • Fix leaks and replace damaged vacuum hoses or charge pipes
  • Replace the wastegate actuator or turbocharger if a mechanical fault is confirmed
  • Reflash or replace the ECM only after ruling out everything else

Questions and answers

What does P0048 mean?

The ECM detected a high signal in boost control circuit "A". The most common culprits are the boost control solenoid or its wiring.

Can I drive with a P0048 code?

Briefly and gently, since power is likely limited. Get it diagnosed soon to avoid damaging the turbo.

How do I fix P0048?

Start with the wiring, connector and vacuum hoses, then test the boost solenoid. If those are fine, check the wastegate or variable-geometry mechanism.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.