Fuel and air

P0242 — Turbo/Supercharger Boost Sensor 'B' Circuit High

Severity: medium Drive with care, to a shop

What P0242 means

The engine control module constantly monitors boost sensor 'B', which measures air pressure after the turbocharger or supercharger. P0242 is set when the signal voltage is higher than the allowed range, for example close to the reference voltage. The module can no longer calculate boost and fueling correctly, so it often limits engine power.

Symptoms

  • Check Engine light on
  • Reduced boost and engine power
  • Sluggish acceleration
  • Limp mode activated
  • Unstable running under load
  • Unusual turbocharger noise

Possible causes

  1. Failed boost pressure sensor 'B'
  2. Open signal wire or poor connector contact at the sensor
  3. Signal wire shorted to power
  4. Open ground or lost 5 V reference at the sensor
  5. Faulty wastegate actuator or boost control valve
  6. Failed ECM (rare)

How to diagnose

  1. Scan all codes and freeze frame data, note them, clear the code and see whether it returns
  2. In live data, compare the boost sensor reading with key on, engine off against barometric pressure
  3. Inspect the sensor connector and harness for chafing, corrosion, moisture and pushed-out pins
  4. Use a multimeter to check 5 V reference, ground and signal wire for a short to power
  5. Check boost hoses and vacuum lines for cracks and leaks
  6. Compare specified and actual boost during acceleration
  7. Check turbo actuator and boost control valve movement over the full range
  8. If wiring and sensor are good, test the ECM and check for software updates

Common fixes

  • Replace boost pressure sensor 'B'
  • Repair damaged wiring or replace the connector
  • Repair or replace the wastegate actuator or boost control valve
  • Reflash or replace the ECM if testing confirms it is faulty

Questions and answers

What does P0242 mean?

The ECM is getting a too-high voltage signal from boost pressure sensor 'B'. The cause may be the sensor, the wiring, or rarely the control module.

Can I drive with P0242?

Only briefly and without heavy load. The engine usually loses power, and extended driving can lead to turbo stress and mixture problems.

What most often causes P0242?

A failed boost pressure sensor or damaged wiring shorted to power is the most common cause. Start by inspecting the connector and checking voltage at the sensor.

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.