Fuel and air

P0238 — Turbocharger Boost Sensor A Circuit High Input

Severity: medium Drive with care, to a shop

What P0238 means

The engine control module monitors the signal from turbocharger or supercharger boost sensor A, which normally varies smoothly with intake pressure. P0238 sets when that signal voltage goes above the expected range. Causes include a short to power, an open ground, a failed sensor, or a real over-boost condition.

Symptoms

  • Check Engine light on
  • Noticeable loss of power and sluggish acceleration
  • Limp mode
  • Low or erratic boost
  • Hesitation or surging under throttle
  • Unusual noise from the turbo area (sometimes)

Possible causes

  1. Failed boost sensor A
  2. Damaged or corroded sensor wiring or connector
  3. Signal wire shorted to 5 V reference or battery voltage
  4. Open sensor ground circuit
  5. Faulty ECM input circuit (uncommon)
  6. Real over-boost from a stuck wastegate, actuator or boost control solenoid failure
  7. Disconnected or damaged sensor hose, if the sensor uses one

How to diagnose

  1. Scan for codes and freeze frame data, and look for other boost or MAP codes
  2. Inspect the sensor connector and harness for corrosion, moisture, chafing and loose pins
  3. With key on, engine off, compare commanded and actual boost in live data; it should read near atmospheric pressure
  4. Test the 5 V reference and ground at the sensor connector with a multimeter
  5. Check the signal wire for a short to power or an open back to the ECM
  6. Inspect sensor hoses and ports for cracks or blockage
  7. Check wastegate or variable-geometry actuator movement through its full range, and test the boost control solenoid
  8. If wiring tests good, replace the sensor, clear the code and confirm it doesn't return

Common fixes

  • Replace boost sensor A
  • Repair or replace damaged wiring and connectors
  • Repair or replace the wastegate, actuator or boost control solenoid
  • Replace cracked or blocked sensor hoses
  • Repair, replace or reprogram the ECM only if its input circuit is confirmed faulty (rare)

Questions and answers

Can I drive with P0238?

Only carefully and to a repair shop. The engine will likely run with reduced power. If you suspect real over-boost, stop driving.

What most often causes P0238?

Usually the boost sensor itself or its wiring: a corroded connector, an open ground, or a signal wire shorted to power. Real over-boost is less common.

Will P0238 go away if I clear it?

Clearing only turns the light off for a while. If the fault is still present, the code returns as soon as the ECM sees the high signal again.

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.